A simple method for the fabrication of ultrathin films containing low molecular weight dye material is introduced(post-adsorption technique). The chromophore used is 4-nitro-4'-decyloxy azobenzene quaternary ammon...A simple method for the fabrication of ultrathin films containing low molecular weight dye material is introduced(post-adsorption technique). The chromophore used is 4-nitro-4'-decyloxy azobenzene quaternary ammonium salt (azo-10Q).In classical layer-by-layer (LBL) procedures, where the substrate is dipped alternately into the chromophore solution and thecomplementary polyelectrolyte, the chromophore tends to desorb from the film during subsequent immersion in thepolyanion solution, and there is little or no indication of multilayer growth. The extent of desorption depends somewhat onthe selection of polyelectrolyte, the ionic strength and the pH of solution. An alternative approach is to first prepareconventional LBL films from a pair of oppositely charged polyelectrolytes, and then to soak this film into the chromophoresolution, where adsorption by penetration into the LBL film may take place. In preliminary results, a linear dependence ofUV absorbance on layer number of LBL film thus prepared was found, demonstrating the apparent effectiveness of the post-adsorption technique for the preparation of azo-10Q-containing ultrathin films.展开更多
A new method for the production of nanoscaled polymeric multilayer films of ferroelectric PVDF is presented.The ultrathin multilayer films of poly diallyldimethylammonium chloride (PDDA) and polyvinylidene fluoride (P...A new method for the production of nanoscaled polymeric multilayer films of ferroelectric PVDF is presented.The ultrathin multilayer films of poly diallyldimethylammonium chloride (PDDA) and polyvinylidene fluoride (PVDF) have been prepared on fuzed quartz substrate by the layer-by-layer self-assembly (LbL-SA) method.The PDDA/PVDF multilayer films with the thickness of 30 nm to 150 nm have been characterized by quartz crystal microbalance (QCM) and infrared spectra (IR) The QCM reveals that the alternant ultrathin films of PVDF and PDDA are well order assembled.The electric property of the ultrathin PDDA/PVDF multilayer films at room temperature is investigated.Experimental results show that property of ultrathin films differed from that of the thick films.展开更多
We report scanning tunneling microscopy investigation on epitaxial ultrathin films of pyrite-type copper disulfide.Layer-by-layer growth of CuS_(2 )films with a preferential orientation of(111)on SrTiO_3(001)and...We report scanning tunneling microscopy investigation on epitaxial ultrathin films of pyrite-type copper disulfide.Layer-by-layer growth of CuS_(2 )films with a preferential orientation of(111)on SrTiO_3(001)and Bi_2Sr_2Ca Cu_2O_(8+)substrates is achieved by molecular beam epitaxy growth.For ultrathin films on both kinds of substrates,we observe symmetric tunneling gap around the Fermi level that persists up to^15 K.The tunneling gap degrades with either increasing temperature or increasing thickness,suggesting new matter states at the extreme twodimensional limit.展开更多
We present a systematic investigation of magnetic anisotropy induced by oblique deposition of Co thin films on MgO(001) substrates by molecular beam epitaxy at different deposition angles,i.e.,0?,30?,45?,60?,and...We present a systematic investigation of magnetic anisotropy induced by oblique deposition of Co thin films on MgO(001) substrates by molecular beam epitaxy at different deposition angles,i.e.,0?,30?,45?,60?,and 75?with respect to the surface normal.Low energy electron diffraction(LEED),surface magneto–optical Kerr effect(SMOKE),and anisotropic magnetoresistance(AMR) setups were employed to investigate the magnetic properties of cobalt films.The values of in-plane uniaxial magnetic anisotropy(UMA) constant Ku and four-fold magnetocrystalline anisotropy constant K1 were derived from magnetic torque curves on the base of AMR results.It was found that the value of Ku increases with increasing deposition angle with respect to the surface normal,while the value of K_1 remains almost constant for all the samples.Furthermore,by using MOKE results,the Ku values of the films deposited obliquely were also derived from the magnetization curves along hard axis.The results of AMR method were then compared with that of hard axis fitting method(coherent rotation) and found that both methods have almost identical values of UMA constant for each sample.展开更多
In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80:20)with ultrasonication and ...In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80:20)with ultrasonication and the addition of the nucleating agent bicycle[2.2.1]heptane-2,3-dicarboxylic acid disodium salt(HPN-68L)on glass,Si wafers and indium tin oxide(ITO)substrates.The electrical and mechanical properties of the P3HT-T ultrathin films were investigated,and it was found that the conductivity and crack onset strain(COS)were simultaneously improved in comparison with those of the corresponding pristine P3HT film(P3HT-0,without ultrasonication and nucleating agent)on the same substrate,regardless of what substrate was used.Moreover,the conductivity of P3HT-T ultrathin films on different substrates was similar(varying from 3.7 S·cm^(-1)to 4.4 S·cm^(-1)),yet the COS increased from 97%to 138%by varying the substrate from a Si wafer to ITO.Combining grazing-incidence wide-angle X-ray diffraction(GIXRD),UV-visible(UV-Vis)spectroscopy and atomic force microscopy(AFM),we found that the solid order and crystallinity of the P3HT-T ultrathin film on the Si wafer are highest,followed by those on glass,and much lower on ITO.Finally,the surface energy and roughness of three substrates were investigated,and it was found that the polar component of the surface energyγp plays a critical role in determining the crystalline microstructures of P3HT ultrathin films on different substrates.Our work indicates that the P3HT ultrathin film can obviously improve the stretchability and simultaneously retain similar electrical performance when a suitable substrate is chosen.These findings offer a new direction for research on stretchable CP ultrathin films to facilitate future practical applications.展开更多
The defect distribution across an ultrathin film CdTe layer of a CdS/CdTe solar cell is modelled by solving the balance equation in steady state. The degradation of the device parameters due to the induced defects dur...The defect distribution across an ultrathin film CdTe layer of a CdS/CdTe solar cell is modelled by solving the balance equation in steady state. The degradation of the device parameters due to the induced defects during ion implantation is considered where the degradation rate is accelerated if the defect distribution is considerable.The defect concentration is maximum at the surface of the CdTe layer where implantation is applied and it is minimum at the junction with the CdS layer. It shows that ultrathin devices degrade faster if the defect concentration is high at the junction rather than the back region(CdTe/Metal). Since the front and back contacts of the device are close in ultrathin films and the electric field is strong to drive the defects into the junction, the p-doping process might be precisely controlled during ion implantation. The modeling results presented here are in agreement with the few available experimental reports in literature about the degradation and defect configuration of the ultrathin CdTe films.展开更多
In this work, ultrathin pure HfO_2 and Al-doped HfO_2films(about 4-nm thick) are prepared by atomic layer deposition and the crystallinities of these films before and after annealing at temperatures ranging from 550...In this work, ultrathin pure HfO_2 and Al-doped HfO_2films(about 4-nm thick) are prepared by atomic layer deposition and the crystallinities of these films before and after annealing at temperatures ranging from 550℃ to 750℃ are analyzed by grazing incidence x-ray diffraction. The as-deposited pure HfO_2 and Al-doped HfO_2 films are both amorphous. After550-℃ annealing, a multiphase consisting of a few orthorhombic, monoclinic and tetragonal phases can be observed in the pure HfO_2 film while the Al-doped HfO_2 film remains amorphous. After annealing at 650℃ and above, a great number of HfO_2 tetragonal phases, a high-temperature phase with higher dielectric constant, can be stabilized in the Al-doped HfO_2 film. As a result, the dielectric constant is enhanced up to about 35. The physical mechanism of the phase transition behavior is discussed from the viewpoint of thermodynamics and kinetics.展开更多
The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer (ML) grown on Si(111) have been investigated by ferromagnetic resonance (FMR) and vibrating sample mag...The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer (ML) grown on Si(111) have been investigated by ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM). Owing to the significant modification of the energy surface in remanent state by slight misorientation from (111) plane and a uniaxial magnetic anisotropy, the azimuthal angular dependence of in-plane resonance field shows a six-fold symmetry with a weak uniaxial contribution, while the remanence of hysteresis loops displays a two-fold one. The competition between the first and second magnetoerystalline anisotropies may result in the switching of in-plane easy axis of the system. Combining the FMR and VSM measurements, the magnetization reversal mechanism has also been determined.展开更多
In this paper we investigate the formations and morphological stabilities of Co-silicide fihns using 1-8-nm thick Co layers sputter-deposited on silicon (100) substrates. These ultrathin Co-silicide films are formed...In this paper we investigate the formations and morphological stabilities of Co-silicide fihns using 1-8-nm thick Co layers sputter-deposited on silicon (100) substrates. These ultrathin Co-silicide films are formed via solid-state reaction of the deposited Co films with Si substrate at annealing temperatures from 450 ℃ to 850 ℃. For a Co layer with a thickness no larger than i nm, epitaxially aligned CoSi2 films readily grow on silicon (100) substrate and exhibit good morphological stabilities up to 600 ℃. For a Co layer thicker than 1 nm, polycrystalline CoSi and CoSi2 films are observed. The critical thickness below which epitaxially aligned CoSi2 film prevails is smaller than the reported critical thickness of the Ni layer for epitaxial alignment of NiSi2 on silicon (100) substrate. The larger lattice mismatch between the CoSi2 film and the silicon substrate is the root cause for the smaller critical thickness of the Co layer.展开更多
We have investigated the crystallization and morphological behaviors of poly(ε-caprolactone)-b-poly(L-lactide) (PCL-b-PLLA) in its autophobic dewetted ultrathin films (-11 nm) using atomic force microscopy (...We have investigated the crystallization and morphological behaviors of poly(ε-caprolactone)-b-poly(L-lactide) (PCL-b-PLLA) in its autophobic dewetted ultrathin films (-11 nm) using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The autophobic dewetting process creates a well defined film geometry containing an extremely thin wetting layer (-4.5 nm) with densely distributed micrometer droplets atop, which re- stricts the primary nucleation process to occurring only in the droplets. In addition to the normally encountered flat-on lamellae, the growth of edge-on lamellae in such a thin wetting layer has been observed on both of two crys- tallization paths. In thermal crystallization, flat-on lamellae are favored at small supercoolings while edge-on la- mellae appear at very large supercoolings both in the droplets and the wetting layer. For cold crystallization, the edge-on lamellae can form easily in the droplets and grow into the wetting layer even at very small supercoolings. These observations are explained on the basis that the nucleation and lamellar orientation are strongly affected by the film geometry, the crystallization paths, and the applied supercoolings.展开更多
In recent years,immense interest has been paid to the biomolecular architecture with the aim of protein assembly in two dimensions on solid substrates,and the constructions of clay-protein ultrathin films(CPUFs) are p...In recent years,immense interest has been paid to the biomolecular architecture with the aim of protein assembly in two dimensions on solid substrates,and the constructions of clay-protein ultrathin films(CPUFs) are particularly concerned.This paper gives an overview of the recent research concerning the protein molecules(lysozyme,papain,protamine,bovine serum albumin) immobilized on clay mineral(Na-saponite) platelets and assembled in monolayered or multilayered hybrid ultrafilms or nanofilms.Two techniques including alternate layer-by-layer(LbL) assembly and the Langmuir-Blodgett(LB) are described in detail.A variety of means,including UV-vis absorption,attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy,XRD,AFM and surface chemistry techniques,have been described for characterization of the films in terms of quantification of protein and clay.The result reveals that electrostatic interaction is a prominent but not the only driving force in CPUF construction.In the case of LB technique,we managed to manipulate the elementary clay mineral platelets(1.3 nm in thickness) and assemble proteins into CPUFs with the aid of surfactants,and the formation of CPUFs was monitored via surface pressure vs.time(π-t) kinetics curves and surface pressure vs.area(π-A) isotherms.The factors that influence protein adsorption on the clay layer,such as surfactants,the concentration of clay,equilibrium time,categories of protein,and injection methods,were investigated.The parameters such as protein amount(nS),packing density(■),and average surface area per molecule(Ω) of deposited CPUFs were measured via method of surface chemistry and spectroscopy.By comparing the results of surface chemistry with those of adsorption experiments,we demonstrate that the surface chemistry method is a useful tool in investigating CPUFs.We also found that the water soluble protein molecules could form protein-clay hybrid monolayer over the dilute clay dispersions without addition of surfactants,and CPUFs containing elementary clay sheets and protein with great homogeneity were easily prepared by controlling certain surface pressure.To investigate the bio-catalytic performance of the immobilized lysozyme in CPUFs,we deposited CPUFs onto a cover glass,and installed the cover glass in a flow cell-grown reactor for Comamonas testosteroni(WDL7-GFP) incubation.The results show that the proliferation of WDL7-GFP is greatly suppressed by lysozyme,which demonstrates that lysozyme still retains its bioactivity after it is immobilized in the CPUFs.展开更多
A dispersion compensation method is introduced to correct the distorted image passing through an ultrathin metal film.An LCD-CCD system is modeled by the back propagation network and used to evaluate the transmittance...A dispersion compensation method is introduced to correct the distorted image passing through an ultrathin metal film.An LCD-CCD system is modeled by the back propagation network and used to evaluate the transmittance of the ultrathin metal film.Training samples for the network come from 729 images captured by shooting test patches,in which the RGB values are uniformity distributed between 0 and 255.The RGB value of the original image that will be distorted by the dispersion is first transformed by mapping from the LCD to the CCD,multiplied by the inverse matrix of the transmittance matrix,and finally transformed by mapping from the CCD to the LCD,then the corrected image is obtained.In order to verify the effectiveness of the proposed method,ultrathin aluminum films with different thicknesses are evaporated on glass substrates and laid between the CCD and LCD.Experimental results show that the proposed method compensates for the dispersion successfully.展开更多
We discuss the surface plasmon-polaritons used for ultrathin metal films with the aid of linear response theory and make comparisons with the known result given by Economou E N. In this paper we consider transverse el...We discuss the surface plasmon-polaritons used for ultrathin metal films with the aid of linear response theory and make comparisons with the known result given by Economou E N. In this paper we consider transverse electromagnetic fields and assume that the electromagnetic field in the linear response formula is the induced field due to the current of the electrons. It satisfies the Maxwell equation and thus we replace the current (charge) term in the Maxwell equation with the linear response expectation value. Finally, taking the external field to be zero, we obtain the dispersion relation of the surface plasmons from the eigenvalue equation. In addition, the charge-density and current-density in the z direction on the surface of ultrathin metal films are also calculated. The results may be helpful to the fundamental understanding of the complex phenomenon of surface plasmon-polaritons.展开更多
We review recent studies by different experimental means of ultrathin films,exhibiting thickness-driven spin reorientation transitions(SRTs).The stage is set by determining,via phenomenological thermodynamic descripti...We review recent studies by different experimental means of ultrathin films,exhibiting thickness-driven spin reorientation transitions(SRTs).The stage is set by determining,via phenomenological thermodynamic description,of the relevant phase diagrams for the possible types of SRT with and without applied magnetic field.Suitable representation may be chosen such that best use is made of the linear character(under thickness variation) of the system's path in anisotropy space.The latter involves higher-order bulk and surface anisotropies in a substantial way.We examine sensitive experimental techniques for the detection and quantification of SRTs,such as hysteresis measurements with magneto-optical Kerr effect(MOKE),micromagnetic studies utilizing scanning electron microscopy with polarization analysis(SEMPA),photoemission electron microscopy(PEEM) and spin-polarized low-energy electron microscopy(SPLEEM) as well as ac magnetic susceptibility measurements via MOKE.Key issues are conclusively discussed including the identification of reliable experimental fingerprints about whether a given SRT proceeds via a phase of coexistence or via a cone(canted) phase.We demonstrate how the application of the general theoretical ideas to carefully designed measurements leads to the determination of the most important material parameters in any ultrathin-film SRT,namely,the surface(interface) magnetic anisotropy constants.The review concludes by our personal outline for future promising work on SRTs.展开更多
Highly oriented ultrathin polyethylene (PE) films were prepared by a melt-draw technique. Transmission electron microscopy study on the obtained ultrathin films indicates that the melt drawn PE thin films consist of h...Highly oriented ultrathin polyethylene (PE) films were prepared by a melt-draw technique. Transmission electron microscopy study on the obtained ultrathin films indicates that the melt drawn PE thin films consist of highly oriented edge-on lamellae aligned perpendicular to the drawing direction. Electron diffraction confirms that the PE chains in crystal-line phase are highly oriented in film plane along the drawing direction, while only a random orientation of the crystallographic a-and b-axes can be described through electron diffraction. The IR results on the melt-drawn ultrathin PE films demonstrate that the PE molecular chains in both crystalline and amorphous phases of the melt drawn thin films are well oriented along the drawing direction. Moreover, the IR results indicate that in the crystalline phase, the crystallographic b-axis tend to lie in the thin film plane, while in the amorphous phase, the skeleton plane of some local chains prefers to parallel the film plane. The alignment of b-axis of PE crystals in ultrathin films originates from the fact that the b-axis is the fastest growth direction of the PE crystals.展开更多
The ultrathin aluminum films with thickness in the range of 2~60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/V...The ultrathin aluminum films with thickness in the range of 2~60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/VIS spectrophotometer. The optical constant (n, k) and permittivity (ε', ε') were determined by applying Newton-Simpson recurrent substitution method. The results indicate that the electromagnetic constitutive characteristic of ultrathin aluminum films is a function of thickness and has obvious size effect.展开更多
Results of investigations of band structure, Fermi surface and effective masses of charge carriers in the ultrathin (monolayer graphene)/MnO(001) and MnO(001) films are presented using the method of the density functi...Results of investigations of band structure, Fermi surface and effective masses of charge carriers in the ultrathin (monolayer graphene)/MnO(001) and MnO(001) films are presented using the method of the density functional theory. Features of spin states of valence band and Fermi level as well as an interatomic interaction in these systems are discussed. A magnetic moment at Mn atom is estimated and an effect of spin polarization at atoms of oxygen and carbon has been revealed which natures are discussed. By calculations of structural energies for 2D (monolayer graphene)/MnO(001) and 2D MnO(001) a stability of these systems has been ascertained. In the 2D (monolayer graphene)/MnO(001) and 2D MnO(001) systems the band structure calculations for the 2D systems mentioned above point out that tensor components of effective masses of both electrons and holes are in the ranges of (0.15 - 0.54) m0 and (0.38 - 1.27) m0 respectively. Mobility estimations of two-dimensional charge carriers for a 2D (monolayer graphene)/MnO(001)AF2 heterostructure have been performed.展开更多
It has been shown by thermodynamic and electro-chemical methods that coordination interactions are involved in the process of incorporation of rare-earth elements and/or Fe into Langmuir monolayers of oligomer with al...It has been shown by thermodynamic and electro-chemical methods that coordination interactions are involved in the process of incorporation of rare-earth elements and/or Fe into Langmuir monolayers of oligomer with alkyl fragment. A coordination mechanism, which is responsible for self-organization of octahedral Fe(II)-complexes of nano-cyclic ligands obtained from oligomer of thiophene pyrrole series derivatives in compressed Langmuir monolayers has been proposed. It has been established that a coordinational-polymeric hexagonal network of nano-cyclic ligands with metal centers is formed at the phase transition when compressing the Langmuir monolayers of thiophene pyrrole series oligomer with alkyl fragment on surface of subphase with rare-earth (Sm, Er, Ce) and/or Fe ions.展开更多
基金The financial support of NSERC (Canada) and FCAR (Quebec) is gratefully acknowledged.
文摘A simple method for the fabrication of ultrathin films containing low molecular weight dye material is introduced(post-adsorption technique). The chromophore used is 4-nitro-4'-decyloxy azobenzene quaternary ammonium salt (azo-10Q).In classical layer-by-layer (LBL) procedures, where the substrate is dipped alternately into the chromophore solution and thecomplementary polyelectrolyte, the chromophore tends to desorb from the film during subsequent immersion in thepolyanion solution, and there is little or no indication of multilayer growth. The extent of desorption depends somewhat onthe selection of polyelectrolyte, the ionic strength and the pH of solution. An alternative approach is to first prepareconventional LBL films from a pair of oppositely charged polyelectrolytes, and then to soak this film into the chromophoresolution, where adsorption by penetration into the LBL film may take place. In preliminary results, a linear dependence ofUV absorbance on layer number of LBL film thus prepared was found, demonstrating the apparent effectiveness of the post-adsorption technique for the preparation of azo-10Q-containing ultrathin films.
文摘A new method for the production of nanoscaled polymeric multilayer films of ferroelectric PVDF is presented.The ultrathin multilayer films of poly diallyldimethylammonium chloride (PDDA) and polyvinylidene fluoride (PVDF) have been prepared on fuzed quartz substrate by the layer-by-layer self-assembly (LbL-SA) method.The PDDA/PVDF multilayer films with the thickness of 30 nm to 150 nm have been characterized by quartz crystal microbalance (QCM) and infrared spectra (IR) The QCM reveals that the alternant ultrathin films of PVDF and PDDA are well order assembled.The electric property of the ultrathin PDDA/PVDF multilayer films at room temperature is investigated.Experimental results show that property of ultrathin films differed from that of the thick films.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11574174,11774193 and 11790311the National Basic Research Program of China under Grant No 2015CB921000
文摘We report scanning tunneling microscopy investigation on epitaxial ultrathin films of pyrite-type copper disulfide.Layer-by-layer growth of CuS_(2 )films with a preferential orientation of(111)on SrTiO_3(001)and Bi_2Sr_2Ca Cu_2O_(8+)substrates is achieved by molecular beam epitaxy growth.For ultrathin films on both kinds of substrates,we observe symmetric tunneling gap around the Fermi level that persists up to^15 K.The tunneling gap degrades with either increasing temperature or increasing thickness,suggesting new matter states at the extreme twodimensional limit.
基金Project supported by the Chinese Academy of Sciences–The World Academy of Sciences(CAS–TWAS)Fellowship Programthe National Basic ResearcProgram of China(Grant Nos.2015CB921403 and 2012CB933102)the National Natural Science Foundation of China(Grant Nos.51427801,1137435and 11274361)
文摘We present a systematic investigation of magnetic anisotropy induced by oblique deposition of Co thin films on MgO(001) substrates by molecular beam epitaxy at different deposition angles,i.e.,0?,30?,45?,60?,and 75?with respect to the surface normal.Low energy electron diffraction(LEED),surface magneto–optical Kerr effect(SMOKE),and anisotropic magnetoresistance(AMR) setups were employed to investigate the magnetic properties of cobalt films.The values of in-plane uniaxial magnetic anisotropy(UMA) constant Ku and four-fold magnetocrystalline anisotropy constant K1 were derived from magnetic torque curves on the base of AMR results.It was found that the value of Ku increases with increasing deposition angle with respect to the surface normal,while the value of K_1 remains almost constant for all the samples.Furthermore,by using MOKE results,the Ku values of the films deposited obliquely were also derived from the magnetization curves along hard axis.The results of AMR method were then compared with that of hard axis fitting method(coherent rotation) and found that both methods have almost identical values of UMA constant for each sample.
基金supported by the National Natural Science Foundation of China(No.21975029)。
文摘In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80:20)with ultrasonication and the addition of the nucleating agent bicycle[2.2.1]heptane-2,3-dicarboxylic acid disodium salt(HPN-68L)on glass,Si wafers and indium tin oxide(ITO)substrates.The electrical and mechanical properties of the P3HT-T ultrathin films were investigated,and it was found that the conductivity and crack onset strain(COS)were simultaneously improved in comparison with those of the corresponding pristine P3HT film(P3HT-0,without ultrasonication and nucleating agent)on the same substrate,regardless of what substrate was used.Moreover,the conductivity of P3HT-T ultrathin films on different substrates was similar(varying from 3.7 S·cm^(-1)to 4.4 S·cm^(-1)),yet the COS increased from 97%to 138%by varying the substrate from a Si wafer to ITO.Combining grazing-incidence wide-angle X-ray diffraction(GIXRD),UV-visible(UV-Vis)spectroscopy and atomic force microscopy(AFM),we found that the solid order and crystallinity of the P3HT-T ultrathin film on the Si wafer are highest,followed by those on glass,and much lower on ITO.Finally,the surface energy and roughness of three substrates were investigated,and it was found that the polar component of the surface energyγp plays a critical role in determining the crystalline microstructures of P3HT ultrathin films on different substrates.Our work indicates that the P3HT ultrathin film can obviously improve the stretchability and simultaneously retain similar electrical performance when a suitable substrate is chosen.These findings offer a new direction for research on stretchable CP ultrathin films to facilitate future practical applications.
文摘The defect distribution across an ultrathin film CdTe layer of a CdS/CdTe solar cell is modelled by solving the balance equation in steady state. The degradation of the device parameters due to the induced defects during ion implantation is considered where the degradation rate is accelerated if the defect distribution is considerable.The defect concentration is maximum at the surface of the CdTe layer where implantation is applied and it is minimum at the junction with the CdS layer. It shows that ultrathin devices degrade faster if the defect concentration is high at the junction rather than the back region(CdTe/Metal). Since the front and back contacts of the device are close in ultrathin films and the electric field is strong to drive the defects into the junction, the p-doping process might be precisely controlled during ion implantation. The modeling results presented here are in agreement with the few available experimental reports in literature about the degradation and defect configuration of the ultrathin CdTe films.
基金Project supported by the National High Technology Research and Development Program of China(Grant No.2015AA016501)the National Natural Science Foundation of China(Grant Nos.61574168 and 61504163)
文摘In this work, ultrathin pure HfO_2 and Al-doped HfO_2films(about 4-nm thick) are prepared by atomic layer deposition and the crystallinities of these films before and after annealing at temperatures ranging from 550℃ to 750℃ are analyzed by grazing incidence x-ray diffraction. The as-deposited pure HfO_2 and Al-doped HfO_2 films are both amorphous. After550-℃ annealing, a multiphase consisting of a few orthorhombic, monoclinic and tetragonal phases can be observed in the pure HfO_2 film while the Al-doped HfO_2 film remains amorphous. After annealing at 650℃ and above, a great number of HfO_2 tetragonal phases, a high-temperature phase with higher dielectric constant, can be stabilized in the Al-doped HfO_2 film. As a result, the dielectric constant is enhanced up to about 35. The physical mechanism of the phase transition behavior is discussed from the viewpoint of thermodynamics and kinetics.
基金Project supported by the National Basic Resea.rch Program of China (Grant Nos. 2009CB929201, 2010CB934202, and 2011CB921801) and the National Natural Science Foundation of China (Grant Nos. 50931006, 11034004, and 51021061).
文摘The magnetic anisotropy and magnetization reversal of single crystal Fe films with thickness of 45 monolayer (ML) grown on Si(111) have been investigated by ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM). Owing to the significant modification of the energy surface in remanent state by slight misorientation from (111) plane and a uniaxial magnetic anisotropy, the azimuthal angular dependence of in-plane resonance field shows a six-fold symmetry with a weak uniaxial contribution, while the remanence of hysteresis loops displays a two-fold one. The competition between the first and second magnetoerystalline anisotropies may result in the switching of in-plane easy axis of the system. Combining the FMR and VSM measurements, the magnetization reversal mechanism has also been determined.
基金Project supported by the "China National Science and Technology Major Project 02" (Grant No. 2009ZX02035-003)the National Natural Science Foundation of China (Grant No. 61176090)the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning
文摘In this paper we investigate the formations and morphological stabilities of Co-silicide fihns using 1-8-nm thick Co layers sputter-deposited on silicon (100) substrates. These ultrathin Co-silicide films are formed via solid-state reaction of the deposited Co films with Si substrate at annealing temperatures from 450 ℃ to 850 ℃. For a Co layer with a thickness no larger than i nm, epitaxially aligned CoSi2 films readily grow on silicon (100) substrate and exhibit good morphological stabilities up to 600 ℃. For a Co layer thicker than 1 nm, polycrystalline CoSi and CoSi2 films are observed. The critical thickness below which epitaxially aligned CoSi2 film prevails is smaller than the reported critical thickness of the Ni layer for epitaxial alignment of NiSi2 on silicon (100) substrate. The larger lattice mismatch between the CoSi2 film and the silicon substrate is the root cause for the smaller critical thickness of the Co layer.
文摘We have investigated the crystallization and morphological behaviors of poly(ε-caprolactone)-b-poly(L-lactide) (PCL-b-PLLA) in its autophobic dewetted ultrathin films (-11 nm) using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The autophobic dewetting process creates a well defined film geometry containing an extremely thin wetting layer (-4.5 nm) with densely distributed micrometer droplets atop, which re- stricts the primary nucleation process to occurring only in the droplets. In addition to the normally encountered flat-on lamellae, the growth of edge-on lamellae in such a thin wetting layer has been observed on both of two crys- tallization paths. In thermal crystallization, flat-on lamellae are favored at small supercoolings while edge-on la- mellae appear at very large supercoolings both in the droplets and the wetting layer. For cold crystallization, the edge-on lamellae can form easily in the droplets and grow into the wetting layer even at very small supercoolings. These observations are explained on the basis that the nucleation and lamellar orientation are strongly affected by the film geometry, the crystallization paths, and the applied supercoolings.
基金supported by National Natural Science Foundation of China(21103039)Research Fund for the Doctoral Program of Higher Education of China (20110111120008)
文摘In recent years,immense interest has been paid to the biomolecular architecture with the aim of protein assembly in two dimensions on solid substrates,and the constructions of clay-protein ultrathin films(CPUFs) are particularly concerned.This paper gives an overview of the recent research concerning the protein molecules(lysozyme,papain,protamine,bovine serum albumin) immobilized on clay mineral(Na-saponite) platelets and assembled in monolayered or multilayered hybrid ultrafilms or nanofilms.Two techniques including alternate layer-by-layer(LbL) assembly and the Langmuir-Blodgett(LB) are described in detail.A variety of means,including UV-vis absorption,attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy,XRD,AFM and surface chemistry techniques,have been described for characterization of the films in terms of quantification of protein and clay.The result reveals that electrostatic interaction is a prominent but not the only driving force in CPUF construction.In the case of LB technique,we managed to manipulate the elementary clay mineral platelets(1.3 nm in thickness) and assemble proteins into CPUFs with the aid of surfactants,and the formation of CPUFs was monitored via surface pressure vs.time(π-t) kinetics curves and surface pressure vs.area(π-A) isotherms.The factors that influence protein adsorption on the clay layer,such as surfactants,the concentration of clay,equilibrium time,categories of protein,and injection methods,were investigated.The parameters such as protein amount(nS),packing density(■),and average surface area per molecule(Ω) of deposited CPUFs were measured via method of surface chemistry and spectroscopy.By comparing the results of surface chemistry with those of adsorption experiments,we demonstrate that the surface chemistry method is a useful tool in investigating CPUFs.We also found that the water soluble protein molecules could form protein-clay hybrid monolayer over the dilute clay dispersions without addition of surfactants,and CPUFs containing elementary clay sheets and protein with great homogeneity were easily prepared by controlling certain surface pressure.To investigate the bio-catalytic performance of the immobilized lysozyme in CPUFs,we deposited CPUFs onto a cover glass,and installed the cover glass in a flow cell-grown reactor for Comamonas testosteroni(WDL7-GFP) incubation.The results show that the proliferation of WDL7-GFP is greatly suppressed by lysozyme,which demonstrates that lysozyme still retains its bioactivity after it is immobilized in the CPUFs.
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2009AA044001)the Open Funds of the State Key Laboratory of Robotics and Systems (HIT),China (Grant No. SKLRS-2010-MS-01)the Fundamental Research Funds for the Central Universities,China
文摘A dispersion compensation method is introduced to correct the distorted image passing through an ultrathin metal film.An LCD-CCD system is modeled by the back propagation network and used to evaluate the transmittance of the ultrathin metal film.Training samples for the network come from 729 images captured by shooting test patches,in which the RGB values are uniformity distributed between 0 and 255.The RGB value of the original image that will be distorted by the dispersion is first transformed by mapping from the LCD to the CCD,multiplied by the inverse matrix of the transmittance matrix,and finally transformed by mapping from the CCD to the LCD,then the corrected image is obtained.In order to verify the effectiveness of the proposed method,ultrathin aluminum films with different thicknesses are evaporated on glass substrates and laid between the CCD and LCD.Experimental results show that the proposed method compensates for the dispersion successfully.
基金supported by the Cultivation of Innovative Talents of the Colleges and Universities of Guangdong Province of China(Grant No. LYM10098)
文摘We discuss the surface plasmon-polaritons used for ultrathin metal films with the aid of linear response theory and make comparisons with the known result given by Economou E N. In this paper we consider transverse electromagnetic fields and assume that the electromagnetic field in the linear response formula is the induced field due to the current of the electrons. It satisfies the Maxwell equation and thus we replace the current (charge) term in the Maxwell equation with the linear response expectation value. Finally, taking the external field to be zero, we obtain the dispersion relation of the surface plasmons from the eigenvalue equation. In addition, the charge-density and current-density in the z direction on the surface of ultrathin metal films are also calculated. The results may be helpful to the fundamental understanding of the complex phenomenon of surface plasmon-polaritons.
基金supported by the State Key Programme for Basic Research of China (Grant No. 2010CB923401)National Natural Science Foundation of China (Grant Nos. 10834001,10974087 and 11023002)Natural Science Foundation of Jiangsu (Grant No. BK2012300)
文摘We review recent studies by different experimental means of ultrathin films,exhibiting thickness-driven spin reorientation transitions(SRTs).The stage is set by determining,via phenomenological thermodynamic description,of the relevant phase diagrams for the possible types of SRT with and without applied magnetic field.Suitable representation may be chosen such that best use is made of the linear character(under thickness variation) of the system's path in anisotropy space.The latter involves higher-order bulk and surface anisotropies in a substantial way.We examine sensitive experimental techniques for the detection and quantification of SRTs,such as hysteresis measurements with magneto-optical Kerr effect(MOKE),micromagnetic studies utilizing scanning electron microscopy with polarization analysis(SEMPA),photoemission electron microscopy(PEEM) and spin-polarized low-energy electron microscopy(SPLEEM) as well as ac magnetic susceptibility measurements via MOKE.Key issues are conclusively discussed including the identification of reliable experimental fingerprints about whether a given SRT proceeds via a phase of coexistence or via a cone(canted) phase.We demonstrate how the application of the general theoretical ideas to carefully designed measurements leads to the determination of the most important material parameters in any ultrathin-film SRT,namely,the surface(interface) magnetic anisotropy constants.The review concludes by our personal outline for future promising work on SRTs.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.20425414,20374056,20304018,50521302 and 20423003)the 973 Programs from M0ST of China.
文摘Highly oriented ultrathin polyethylene (PE) films were prepared by a melt-draw technique. Transmission electron microscopy study on the obtained ultrathin films indicates that the melt drawn PE thin films consist of highly oriented edge-on lamellae aligned perpendicular to the drawing direction. Electron diffraction confirms that the PE chains in crystal-line phase are highly oriented in film plane along the drawing direction, while only a random orientation of the crystallographic a-and b-axes can be described through electron diffraction. The IR results on the melt-drawn ultrathin PE films demonstrate that the PE molecular chains in both crystalline and amorphous phases of the melt drawn thin films are well oriented along the drawing direction. Moreover, the IR results indicate that in the crystalline phase, the crystallographic b-axis tend to lie in the thin film plane, while in the amorphous phase, the skeleton plane of some local chains prefers to parallel the film plane. The alignment of b-axis of PE crystals in ultrathin films originates from the fact that the b-axis is the fastest growth direction of the PE crystals.
基金the Advance FOundation of National Defense is greatly appreciated.
文摘The ultrathin aluminum films with thickness in the range of 2~60 nm have been deposited by dc magnetron sputtering apparatus. Reflectance and transmittance of the obtained samples were measured with a WFZ-900-D4 UV/VIS spectrophotometer. The optical constant (n, k) and permittivity (ε', ε') were determined by applying Newton-Simpson recurrent substitution method. The results indicate that the electromagnetic constitutive characteristic of ultrathin aluminum films is a function of thickness and has obvious size effect.
文摘Results of investigations of band structure, Fermi surface and effective masses of charge carriers in the ultrathin (monolayer graphene)/MnO(001) and MnO(001) films are presented using the method of the density functional theory. Features of spin states of valence band and Fermi level as well as an interatomic interaction in these systems are discussed. A magnetic moment at Mn atom is estimated and an effect of spin polarization at atoms of oxygen and carbon has been revealed which natures are discussed. By calculations of structural energies for 2D (monolayer graphene)/MnO(001) and 2D MnO(001) a stability of these systems has been ascertained. In the 2D (monolayer graphene)/MnO(001) and 2D MnO(001) systems the band structure calculations for the 2D systems mentioned above point out that tensor components of effective masses of both electrons and holes are in the ranges of (0.15 - 0.54) m0 and (0.38 - 1.27) m0 respectively. Mobility estimations of two-dimensional charge carriers for a 2D (monolayer graphene)/MnO(001)AF2 heterostructure have been performed.
文摘It has been shown by thermodynamic and electro-chemical methods that coordination interactions are involved in the process of incorporation of rare-earth elements and/or Fe into Langmuir monolayers of oligomer with alkyl fragment. A coordination mechanism, which is responsible for self-organization of octahedral Fe(II)-complexes of nano-cyclic ligands obtained from oligomer of thiophene pyrrole series derivatives in compressed Langmuir monolayers has been proposed. It has been established that a coordinational-polymeric hexagonal network of nano-cyclic ligands with metal centers is formed at the phase transition when compressing the Langmuir monolayers of thiophene pyrrole series oligomer with alkyl fragment on surface of subphase with rare-earth (Sm, Er, Ce) and/or Fe ions.