Structure and electrical properties of polysilicon films doped with ammonium tetraborate tetrahydrate

Here,p-type polysilicon films are fabricated by ex-situ doping method with ammonium tetraborate tetrahydrate(ATT)as the boron source,named ATT-pPoly.The effects of ATT on the properties of polysilicon films are comprehensively analyzed.The Raman spectra reveal that the ATT-pPoly film is composed of grain boundary and crystalline regions.The preferred orientation is the(111)direction.The grain size increases from 16−23 nm to 21−47 nm,by~70%on average.Comparing with other reported films,Hall measurements reveal that the ATT-pPoly film has a higher carrier concentration(>10^(20)cm^(−3))and higher carrier mobility(>30 cm2/(V·s)).The superior properties of the ATT-pPoly film are attributed to the heavy doping and improved grain size.Heavy doping property is proved by the mean sheet resistance(Rsheet,m)and distribution profile.The R_(sheet,m)decreases by more than 30%,and it can be further decreased by 90%if the annealing temperature or duration is increased.The boron concentration of ATT-pPoly film annealed at 950℃ for 45 min is~3×10^(20)cm^(−3),and the distribution is nearly the same,except near the surface.Besides,the standard deviation coefficient(σ)of Rsheet,m is less than 5.0%,which verifies the excellent uniformity of ATT-pPoly film.

A highly sensitive ratiometric near-infrared nanosensor based on erbium-hyperdoped silicon quantum dots for iron(Ⅲ) detection

Ratiometric fluorescent detection of iron(Ⅲ)(Fe^(3+))offers inherent self-calibration and contactless analytic capabilities.However,realizing a dual-emission near-infrared(NIR)nanosensor with a low limit of detection(LOD)is rather challenging.In this work,we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots(Si QDs:Er),which emit NIR light at the wavelengths of 810 and 1540 nm.A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe^(3+)detection with a very low LOD(0.06μM).The effects of pH,recyclability,and the interplay between static and dynamic quenching mechanisms for Fe^(3+)detection have been systematically studied.In addition,we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.

Evaluation on residual stresses of silicon-doped CVD diamond films using X-ray diffraction and Raman spectroscopy

The effect of silicon doping on the residual stress of CVD diamond films is examined using both X-ray diffraction (XRD) analysis and Raman spectroscopy measurements. The examined Si-doped diamond films are deposited on WC-Co substrates in a home-made bias-enhanced HFCVD apparatus. Ethyl silicate (Si(OC2H5)4) is dissolved in acetone to obtain various Si/C mole ratio ranging from 0.1% to 1.4% in the reaction gas. Characterizations with SEM and XRD indicate increasing silicon concentration may result in grain size decreasing and diamond [110] texture becoming dominant. The residual stress values of as-deposited Si-doped diamond films are evaluated by both sin2ψ method, which measures the (220) diamond Bragg diffraction peaks using XRD, with ψ-values ranging from 0° to 45°, and Raman spectroscopy, which detects the diamond Raman peak shift from the natural diamond line at 1332 cm-1. The residual stress evolution on the silicon doping level estimated from the above two methods presents rather good agreements, exhibiting that all deposited Si-doped diamond films present compressive stress and the sample with Si/C mole ratio of 0.1% possesses the largest residual stress of ~1.75 GPa (Raman) or ~2.3 GPa (XRD). As the silicon doping level is up further, the residual stress reduces to a relative stable value around 1.3 GPa.

Doped-Chamber Deposition of Intrinsic Microcrystalline Silicon Thin Films and Its Application in Solar Cells

A series of microcrystalline silicon thin films were fabricated by very high frequency plasma enhanced chemical vapor deposition （VHF-PECVD） at different silane concentrations in a P chamber. Through analysis of the structural and electrical properties of these materials,we conclude that the photosensitivity slightly decreased then increased as the silane concentration increased,while the crystalline volume fraction indicates the opposite change. Results of XRD indicate that thin films have a （220） preferable orientation under certain conditions. Microcrystalline silicon solar cells with conversion efficiency 4. 7% and micromorph tandem solar cells 8.5% were fabricated by VHF-PECVD （p layer and i layer of microcrystalline silicon solar cells were deposited in P chamber）, respectively.

Preparation and photocatalytic activity of neodymium doping titania loaded to silicon dioxide

Neodymium doping titania was loaded to silicon dioxide to prepare Nd/TiO2-SiO2 by sol-gel method and Nd/TiO2-SiO2 was characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, Fourier transform-infrared spectroscopy （FT-IR） and diffuse reflectance spectra （DRS）. Photocatalytic activities of Nd/TiO2-SiO2 with different neodymium contents were evaluated by degradation of methyl orange. The light absorption of Nd/TiO2-SiO2 increased with increasing doping neodymium in a visible light range of 388-619 nm, and Nd doping was in favor of decreasing the recombination of photo-generated electrons with holes. Nd and SiO2 improved the photocatalytic activity of TiO2. The optimal molar fraction of Nd to Ti was 0.1%, and the optimum calcination temperature was 600 ℃. The highest degradation rate of methyl orange was 82.9% after irradiation for 1 h.

Numerical and analytical investigations for the SOI LDMOS with alternated high-k dielectric and step doped silicon pillars

This paper presents a new silicon-on-insulator(SOI) lateral-double-diffused metal-oxide-semiconductor transistor(LDMOST) device with alternated high-k dielectric and step doped silicon pillars(HKSD device). Due to the modulation of step doping technology and high-k dielectric on the electric field and doped profile of each zone, the HKSD device shows a greater performance. The analytical models of the potential, electric field, optimal breakdown voltage, and optimal doped profile are derived. The analytical results and the simulated results are basically consistent, which confirms the proposed model suitable for the HKSD device. The potential and electric field modulation mechanism are investigated based on the simulation and analytical models. Furthermore, the influence of the parameters on the breakdown voltage(BV) and specific on-resistance(R_(on,sp)) are obtained. The results indicate that the HKSD device has a higher BV and lower R_(on,sp) compared to the SD device and HK device.

Preparation, Curing Reactivity and Thermal Properties of Titanium-doped Silicone Resins

Novel titanium-doped silicone resins were synthesized from low-cost silane monomers and tetrabutyl titanate as raw materials and hydrochloric acid as catalyst, with titanium element as dopant into principal chain of Si-O-Si. The resins were characterized by means of FTIR, IH NMR and 13C NMR spectra, their thermal properties and curing properties were investigated and their corresponding films were determined. The results show that the thermal stability and storage stability of the resins were influenced by the types of silane monomers containing dif- ferent carbon atomicities of organic group. The thermal stability of the titanium-doped silicone resin with a molar ratio of silane monomer B（n-propyl triethoxysilane） to silane monomer C（n-octyl triethoxysilane） being 1：1 is superior to that of the resin with a molar ratio of silane monomer B to silane monomer C being 1：3. However, the storage stability of the former is inferior to that of the latter. This work also showed that the synthesized titanium-doped silicone resins have the highest thermal stability up to 450--500℃ with an atomicity molar ratio of 1：4 of titanium to silicon in the reactants. But the best storage stability of the resin prepared from the reactants with an atomicity molar ratio of 1：6[n（Ti）：n（Si）] was obtained. The effect of the type and content of curing agent on the curing properties of the resin was also studied. Moreover, thermal mechanism and curing mechanism were proposed in this work.

Breakdown voltage model and structure realization of a thin silicon layer with linear variable doping on a silicon on insulator high voltage device with multiple step field plates

Based on the theoretical and experimental investigation of a thin silicon layer（TSL） with linear variable doping（LVD） and further research on the TSL LVD with a multiple step field plate（MSFP）,a breakdown voltage（BV） model is proposed and experimentally verified in this paper.With the two-dimensional Poisson equation of the silicon on insulator（SOI） device,the lateral electric field in drift region of the thin silicon layer is assumed to be constant.For the SOI device with LVD in the thin silicon layer,the dependence of the BV on impurity concentration under the drain is investigated by an enhanced dielectric layer field（ENDIF）,from which the reduced surface field（RESURF） condition is deduced.The drain in the centre of the device has a good self-isolation effect,but the problem of the high voltage interconnection（HVI） line will become serious.The two step field plates including the source field plate and gate field plate can be adopted to shield the HVI adverse effect on the device.Based on this model,the TSL LVD SOI n-channel lateral double-diffused MOSFET（nLDMOS） with MSFP is realized.The experimental breakdown voltage（BV） and specific on-resistance（R on,sp） of the TSL LVD SOI device are 694 V and 21.3 ·mm 2 with a drift region length of 60 μm,buried oxide layer of 3 μm,and silicon layer of 0.15 μm,respectively.

Mg doping reduced full width at half maximum of the near-band-edge emission in Mg doped ZnO films

Sol--gol method was employed to synthesize Mg doped ZnO films on Si substrates. The annealing temperature-dependent structure and optical property of the produced samples were studied. An interesting result observed is that increasing Mg concentration in the studied samples induces the full width at half maximum （FWHM） of their near-band-edge （NBE） emission decrease and the defect related emission of the corresponding sample suppresses drastically. The possible mechanism of the observed result is discussed.

Fluorescence Properties of Eu^(3+)/Gd^(3+)/Citric Acid Mixed Complexes Doping in Silicon Rubber Matrix

Series of doped rare earth compiexes-EuxGd(1-x) (CA)3·nH2O (CA = citric acid) were synthesized. Some characterizations were taken for these complexes. The experimental results shows that the doped rare earth complexes have the best fluorescence property when the ratio of Eu and Gd is from 0.7 to 0.3. Silicon rubber-based composites were prepared by mechanical blending the EuxGd(1-x) (CA)3·nH2O and silicon rubber. Then, the fluorescent property of the composites was studied. It is found that the fluorescence intensity of the composites increase linearly with the contents of the rare earth complexes increasing.

Realization of conformal doping on multicrystalline silicon solar cells and black silicon solar cells by plasma immersion ion implantation

Emitted multi-crystalline silicon and black silicon solar cells are conformal doped by ion implantation using the plasma immersion ion implantation （PⅢ） technique. The non-uniformity of emitter doping is lower than 5 %. The secondary ion mass spectrometer profile indicates that the PⅢ technique obtained 100-rim shallow emitter and the emitter depth could be impelled by furnace annealing to 220 nm and 330 nm at 850 ℃ with one and two hours, respectively. Furnace annealing at 850 ℃ could effectively electrically activate the dopants in the silicon. The efficiency of the black silicon solar cell is 14.84% higher than that of the mc-silicon solar cell due to more incident light being absorbed.

Surface Recombination Concept as Applied to Determinate Silicon Solar Cell Base Optimum Thickness with Doping Level Effect

New expressions of back surface recombination of excess minority carriers in the base of silicon solar are expressed dependent on both, the thickness and the diffusion coefficient which is in relationship with the doping rate. The optimum thickness thus obtained from the base of the solar cell allows the saving of the amount of material needed in its manufacture without reducing its efficiency.

Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact （IBC） silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters （doping concentration and thickness） is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si：H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.

Fabrication and characteristics of nitrogen-doped nanocrystalline diamond/p-type silicon heterojunction

Nitrogen-doped nanocrystalline diamond films(N-NDFs)have been deposited on p-type silicon(Si)by microwave plasma chemical vapor deposition.The reaction gases are methane,hydrogen,and nitrogen without the conventional argon(Ar).The N-NDFs were characterized by X-ray diffraction,Raman spectroscopy,and scanning electron microscopy.The grain sizes are of 8~10 nm in dimension.The N-NDF shows n-type behavior and the corresponding N-NDF/p-Si heterojunction diodes are realized with a high rectification ratio of 102 at^7.8 V,and the current density reaches to1.35 A/cm2 at forward voltage of 8.5 V.The findings suggest that fabricated by CH_4/H_2/N_2 without Ar,the N-NDFs and the related rectifying diodes are favorable for achieving high performance diamond-based optoelectronic devices.

Synthesis of nitrogen-doped single-walled carbon nanotubes and monitoring of doping by Raman spectroscopy

Nitrogen-doped single-walled carbon nanotubes （CNx-SWNTs） with tunable dopant concentrations were synthesized by chemical vapor deposition （CVD）, and their structure and elemental composition were characterized by using transmission electron microscopy （TEM） in combination with electron energy loss spectroscopy （EELS）. By comparing the Raman spectra of pristine and doped nanotubes, we observed the doping-induced Raman G band phonon stiffening and 2D band phonon softening, both of which reflect doping-induced renormalization of the electron and phonon energies in the nan- otubes and behave as expected in accord with the n-type doping effect. On the basis of first principles calculations of the distribution of delocalized carrier density in both the pristine and doped nanotubes, we show how the n-type doping occurs when nitrogen heteroatoms are substitutionally incorporated into the honeycomb tube-shell carbon lattice.

Probing Structure, Thermochemistry, Electron Affinity and Magnetic Moment of Dysprosium-doped Silicon Clusters DySi_n(n = 3～10) and Their Anions with Double-hybrid Density Functional Theory

The equilibrium geometries, electronic structures and electronic properties including adiabatic electron affinity（AEA）, vertical detachment energy（VDE）, simulated photoelectron spectroscopy, HOMO-LUMO gap, charge transfer, and magnetic moment for DySi_n（n = 3~10） clusters and their anions were systematically investigated by using the ABCluster global search technique combined with the B3 LYP and B2 PLYP density functional methods. The results showed that the lowest energy structure of neutral DySi_n（n = 3~10） can be regarded as substituting a Si atom of the ground state structure of Si_（n＋1） with a Dy atom. For anions, the extra electron effect on the structure is significant. Starting from n = 6, the lowest energy structures of DySi_n~？（n = 3~10） differ from those of neutral. The ground state is quintuplet electronic state for DySi_n（n = 3~10） excluding DySi_4 and DySi_9, which is a septet electronic state. For anions, the ground state is a sextuplet electronic state. The reliable AEA and VDE of DySi_n（n = 3~10） are reported. Analyses of HOMO-LUMO gaps indicated that doping Dy atom to silicon clusters can improve significantly their photochemical reactivity, especially for DySi_9. Analyses of NPA revealed that the 4 f electrons of Dy in DySi_4, DySi_9, and DySi_n~？ with n = 4 and 6~10 participate in bonding. That is, DySi_nbelongs to the AB type. The 4 f electrons of Dy atom provide substantially the total magnetic moments for DySi_n and their anions. The dissociation energies of Ln（Ln = Pr, Sm, Eu, Gd, Ho, and Dy） fromLn Sin and their anions were evaluated to examine the relative stabilities.

Density of States in Intrinsic and n/p-Doped Hydrogenated Amorphous and Microcrystalline Silicon

Gap states in amorphous hydrogenated silicon (a-Si:H) doped and microcrystalline silicon doped n and p were examined by analysis of subgap absorption spectra obtained by the Constant Photocurrent Method (CPM) and the Photothermal Deflection Spectroscopy (PDS). Assuming a Gaussian distribution of defect states in the gap, broad distribution of states was found in a-Si:H and doped a-Si:H. A dependence of the defect concentration on Fermi energy was detected and analysed by thermodynamic model of defect formation in a-Si:H.

Microstructure of flow pattern defects in boron-doped Czochralski-grown silicon

The morphology and microstructure of flow pattern defects （FPDs） in lightly boron-doped Czochralski-grown silicon （Cz-Si） crystals were investigated using optical microscopy and atomic force microscopy. The experimental results showed that the morphology of FPDs was parabola-like with several steps. Single-type and dual-type voids were found on the tip of FPDs and two heaves exist on the left and right sides of the void. All the results have proved that FPDs were void-type defects. These results are very useful to investigate FPDs in Cz-Si wafers further and explain the annihilation of FPDs during high-temperature annealing.

Enhanced Photovoltaic Properties for Rear Passivated Crystalline Silicon Solar Cells by Fabricating Boron Doped Local Back Surface Field

In order to enhance the p-type doping concentration in the LBSF, boron was added into the aluminum paste and boron doped local back surface field（B-LBSF） was successfully fabricated in this work. Through boron doping in the LBSF, much higher doping concentration was observed for the B-LBSF over the Al-LBSF. Higher doping concentration in the LBSF is expected to lead to better rear passivation and lower rear contact resistance. Based on one thousand pieces of solar cells for each type, it was found that the rear passivated crystalline silicon solar cells with B-LBSF showed statistical improvement in their photovoltaic properties over those with Al-LBSF.

Sustainable silicon anodes facilitated via a double-layer interface engineering: Inner SiOx combined with outer nitrogen and boron co-doped carbon

Silicon-based(Si)materials are promising anodes for lithium-ion batteries(LIBs)because of their ultrahigh theoretical capacity of 4200 mA h g^(−1).However,commercial applications of Si anodes have been hindered by their drastic volume variation(∼300%)and low electrical conductivity.Here,to tackle the drawbacks,a hierarchical Si anode with double-layer coatings of a SiOx inner layer and a nitrogen(N),boron(B)co-doped carbon(C-NB)outer layer is elaborately designed by copyrolysis of Si-OH structures and a H3BO_(3)-doped polyaniline polymer on the Si surface.Compared with the pristine Si anodes(7mA h g^(−1) at 0.5 A g^(−1) after 340 cycles and 340 mA h g^(−1) at 5 A g^(−1)),the modified Si-based materials(Si@SiOx@C-NB nanospheres)present su perior cycling stability(reversible 1301 mA h g^(−1) at 0.5 A g^(−1) after 340 cycles)as well as excellent rate capability(690mA h g^(−1) at 5 A g^(−1))when used as anodes in LIBs.The unique double-layer coating structure,in which the inner amorphous SiOx layer acts as a buffer matrix and the outer defect-rich carbon enhances the electron diffusion of the whole anode,makes it possible to de liver excellent electrochemical properties.These results indicate that our double-layer coating strategy is a promising approach not only for the devel opment of sustainable Si anodes but also for the design of multielement-doped carbon nanomaterials.