PREPARATION OF NANO-CRYSTALLINE Fe-Cu THIN FILMS AND THEIR MAGNETIC PROPERTIES

Fe-Cu thin films of 0.2 mum in thickness with different Cu contents wereprepared by using r.f. magnetron sputtering onto glass substrate. The effect of sputteringparameters, including Ar gas pressure and input rf power, on the structure and magnetic propertieswas investigated. It was found that when the power is lower than 70W, the structure of the filmsremained single bcc-Fe phase with Cu solubility of up to 50at. percent. TEM observations for thebcc-Fe phase showed that the grain size was in the nanometer range of less than 20nm. The coercivityof Fe- Cu films was largely affected by not only Ar gas pressure but also rf power, and reachedabout 2.5Oe in the pressure of 0.67-6.67Pa and in the power of less than 100W. In addition,saturation magnetization, with Cu content less than 60at. percent, was about proportional to thecontent of bcc-Fe. When Cu content was at 60at. percent, however, saturation magnetization was muchsmaller than its calculation value.

Enhanced adhesion of Cu-W thin films by ion beam assisting bombardment implanting

Cu-W thin film with high W content was deposited by dual-target DC-magnetron co-sputtering technology.Effects of the substrates surface treating technique on the adhesive strength of Cu-W thin films were studied.It is found that the technique of ion beam assisting bombardment implanting of W particles can remarkably improve the adhesive property of Cu-W thin films. Indentation and scratching test show that,the critical load is doubled over than the sample only sputter-cleaned by ion beam.The enhancing mechanism of ion beam assisting bombardment implanting of Cu-W thin films was analyzed.With the help of mid-energy Ar+ion beam,W atoms can diffuse into the Fe-substrate surface layer;Fe atoms in the substrate surface layer and W atoms interlace with one another;and microcosmic mechanical meshing and diffusing combination on atom-scale among the Fe and W atoms through the film/substrate interface can be formed.The wettability and thermal expansion properties of the W atoms diffusion zone containing plentiful W atoms are close to those of pure W or W-based Cu-W film.

镶嵌靶磁控溅射Cu-W薄膜的结构与力学性能

为研究W含量对Cu-W薄膜的结构与力学性能的影响,用磁控溅射工艺制备Cu-W薄膜,靶材为镶嵌组合型。薄膜的成份、结构、表面形貌分别选用能谱仪(EDS)、X射线衍射仪(XRD)和高分辨透射电镜(HRTEM)、扫描电镜(SEM)及原子力显微镜(AFM)进行表征。薄膜屈服强度σ_(0.2)和裂纹萌生临界应变ε_(c)、弹性模量E及显微硬度H分别用微小力测试系统和纳米压痕仪进行测试。结果表明,调整W靶的面积占比即可控制薄膜成分,当W靶的面积占比从5%增至25%时,Cu-W薄膜的W含量(原子分数)从2.30%逐渐提高到15.10%,且薄膜中存在fcc Cu(W)亚稳准固溶体。随W含量的增加,Cu-W薄膜的平均晶粒尺寸从28 nm逐渐减小至18 nm,准固溶度从1.30%(原子分数)W逐渐增至9.50%W,薄膜的表面光洁度提高。随W含量的增加,Cu-W薄膜的屈服强度σ_(0.2)和显微硬度H提高较为明显,弹性模量E稍有增加,而裂纹萌生临界应变ε_(c)则减小。Cu-15.10%W薄膜具有最小的平均晶粒尺寸和最高的表面光洁度,其屈服强度、硬度及弹性模量值最高(σ_(0.2)=0.86 GPa、H=6.1 GPa、E=123.5 GPa),裂纹萌生临界应变ε_(c)值为0.84%,综合力学性能最好。

Scaling Behaviors of Surface Roughening of Cu Thin Films Deposited by Oblique Angle Deposition

Cu thin films with different thicknesses were deposited by magnetron sputtering at various oblique angle θ of incidence between the deposition flux and the substrate surface normal.Cross-section microstructure and surface morphology of the films were investigated by scanning electron microscope(SEM)and atomic force microscope(AFM),respectively.Then the scaling behaviors of film surface roughening were analyzed in terms of dynamic scaling theory.With the increasing of the deposition angle θ,the angleφbetween grain growth direction and substrate surface normal increased gradually.With increasing θ in the range of<50°,the roughness exponent α increased from 0.76 to 0.82 and the growth exponent β decreased from 0.42 to 0.35.However,when θ increased to 70°,α and β changed to 0.72 to 0.61,respectively.The evolution of the scaling exponents effectively revealed the fact that the film surface roughening arises from the competition between surface diffusion and shadowing effect.

组合靶共溅射沉积Cu-W复合薄膜的结构与性能

用嵌入组合型靶材,采用磁控共溅射方法,在单晶硅和聚酰亚胺衬底上制备Cu-W复合薄膜。分别运用能谱仪、X射线衍射仪、扫描电镜和原子力显微镜对Cu-W复合薄膜的成份、结构及表面形貌进行分析表征。选用微小力测试系统、纳米压痕仪及四探针仪分别测试复合薄膜的屈服强度σ_(0.2)和裂纹萌生临界应变ε_(c)、显微硬度H及电阻率ρ。结果表明:可通过调整组合型靶材环状溅射刻蚀区内W靶所占的面积比,有效地调控复合薄膜的W含量。随W靶的面积占比从6%增至30%,Cu-W复合薄膜的W含量从2.6 at.%增至16.9 at.%。W在Cu中的固溶度延展,复合膜内存在面心立方(fcc)Cu(W)亚稳固溶体,随复合膜中W含量增加,W在Cu中的固溶度从1.7 at.%W增至10 at.%W,复合膜的平均晶粒从32 nm减小至16 nm,表面光洁度提高。W含量增加时,复合膜的屈服强度σ_(0.2)、显微硬度H及电阻率ρ增加,而裂纹萌生临界应变ε_(c)减小。

Synthesis of Cu_2ZnSnS_4 thin film from mixed solution of Cu_2SnS_3 nanoparticles and Zn ions

The Cu2ZnSnS4 thin film was prepared by a facile solution method without vacuum environment and toxic substance. The formation mechanism of the film was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman scattering measurements. Through cyclic voltammetry and photo-electricity tests, the electrocatalytic activity of the prepared film as the counter electrode of dye-sensitizedsolar cell was also studied. The results show that the mixed precursor solution mainly consists of Cu2SnS3 nanoparticles and Zn ions.After 550 °C annealing process on the precursor film prepared from the mixed solution, Cu2ZnSnS4 thin film is obtained. Besides, itis found that the prepared Cu2ZnSnS4 thin film has the electrocatalytic activity toward the redox reaction of I3?/I? and the dye-sensitized solar cell with the prepared Cu2ZnSnS4 thin film as the counter electrode achieves the efficiency of 1.09%.

The Effect of Annealing Temperature and Reactive Gases on Optical Properties of Cu₂O Thin Films

The Cu2O thin films were synthesized by using RF sputtering technique. Comparisons were made with films created by deposition at room temperature followed by thermal annealing between 100°C and 400°C and using different gases, oxygen (O2) (oxidizing and reactive gas) and nitrogen (N2) (inert gas), besides air. The thickness of the thin films was kept constant, around 2000 Å (Angstrom). In addition, the RF power and pressure deposition were kept constant, as well. The thin films were evaluated for a range of wavelengths between 200 nm and 400 nm (Ultra Violet spectrum), 400 nm and 700 nm (Visible spectrum), 700 nm and 800 nm (Infrared spectrum) for both, optical transmittance and photoluminescence. From the experimental results, the higher annealing temperature and the introduction of nitrogen (N2) gas produced the following results: the optical bandgap for the Cu2O was found to be 2.23 eV and photoluminescence peaks were around 551 nm and 555 nm, which matched the theoretical analyses. Overall, there was a decrease in the optical bandgap of the Cu2O from 2.56 eV at room temperature to 2.23 eV for the film annealed in nitrogen gas at 400°C. This indicates that the Cu2O is a potential candidate in solar cell applications.

磁控共溅射W-Cu复合薄膜的工艺优化及性能研究

采用磁控共溅射沉积工艺,结合正交试验方法制备W-Cu复合薄膜。用扫描电子显微镜(SEM)观察W-Cu复合薄膜表面形貌,能谱仪(EDS)分析复合薄膜成分。微小力测试系统、纳米压痕仪及四探针仪分别测试复合薄膜的屈服强度σ_(0.2)、裂纹萌生临界应变ε_(c)、显微硬度H及电阻率ρ。结果表明,靶功率密度PD、溅射气压P及靶基距D_(TS)这三个工艺参数影响W-Cu复合薄膜的成分、沉积率、微观结构及力学和电学性能。优化的工艺参数为:PD=10 W/cm^(2)、P=2 Pa、D_(TS)=150 mm。该工艺条件下制备的W-Cu复合薄膜中Cu含量为42.2%(原子分数),沉积率6.6 nm/min。其性能为σ_(0.2)=0.86 GPa,ε_(c)=0.62%,H=7.35 GPa,ρ=19.6μΩ·cm。该复合膜微观结构呈均质化特征,W和Cu组元分布均匀。

Effect of Reaction Temperature and Time on the Structural Properties of Cu(In,Ga)Se_2 Thin Films Deposited by Sequential Elemental Layer Technique

Thin films of copper indium gallium selenide Cu（In,Ga）Se2 （CIGS） were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction （XRD） technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time.It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes： 〈450℃, 450-950℃, and 〉950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.

Engineering of electronic and optical properties of ZnO thin films via Cu doping

ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique. XRD analysis indicates that the crystal quality of the ZnO：Cu film can be enhanced by a moderate level of Cu-doping in the sputtering process. The results of XPS spectra of zinc, oxygen, and copper elements show that Cu-doping has an evident and complicated effect on the chemical state of oxygen, but little effect on those of zinc and copper. Interestingly, further investigation of the optical properties of ZnO：Cu samples shows that the transmittance spectra exhibit both red shift and blue shift with the increase of Cu doping, in contrast to the simple monotonic behavior of the Burstein–Moss effect. Analysis reveals that this is due to the competition between oxygen vacancies and intrinsic and surface states of oxygen in the sample. Our result may suggest an effective way of tuning the bandgap of ZnO samples.

A NEW CONCEPT TOWARD INDUSTRIALIZATION OF Cu-III-VI_2 THIN FILM SOLAR CELLS AND SOME PRELIMINARY EXPERIMENT RESULTS

A new concept of full vacuum manufacturing for Cu-III-IV2 thin-film solar cells has been discussed. Cu-III-IV2 thin-film solar cells manufactured using full in- line reactive sputtering will result in lower cost than that of the conventional method with CdS layer fabricated with chemical bath deposition (CBS) method. Us ing reactive sputtering process with organo- metallic gases, the compositions a nd electronic properties of Cu-III-IV2 thin-film can be fine-tuned and precisely controlled. n-type Cu-III-IV2 film and ZnS suffer layer can also be deposited u sing the in-line sputtering instead of using the CdS layer. The environmental po llution problems arising from using CdS can be eliminated and the ultimate goal of full in-line process development can then be realized. Some preliminary exper imental results on a modal solar cell fabricated by the new technique in the new concept have been presented.

Preparation and Characterization of Cu-Zn Nano-Structural Ferrite Thin Films Produced by Pulsed Laser Deposition (PLD)

Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited from the target onto sapphire (001) substrates heated to 650℃ in an oxygen atmosphere of 100 mTorr. The laser beam was incident On the target face at an angle of 45°. Studies on crystal structure were done by X-ray diffactometry (XRD). The surface texture, cross-section morphology and grain size was observed by JEOL-JSM-6400 scanning electron microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) [Model DI 3000, Digital instruments].

Electrodeposition and Characterization of Cu(In, Al)Se₂for Applications in Thin Film Tandem Solar Cells

Cu(In, Al)Se2 thin films were prepared by electrodeposition from the aqueous solution consisting of CuCl2, InCl3, AlCl3 and SeO2 onto ITO coated glass substrates. The as-deposited films were annealed under vacuum for 30 min at temperature ranging between 200°C and 400°C. The structural, composition, morphology, optical band gap and electrical resistivity of elaborated thin films were studied, respectively using x-ray diffraction, energy dispersive analysis of x-ray, scanning electron microscopy, UV spectrophotometer and four-point probe method. The lattice constant and structural parameters viz. crystallite size, dislocation density and strain of the films were also calculated. After vacuum annealing, x-ray diffraction results revealed that all films were polycrystalline in nature and exhibit chalcopyrite structure with (112) as preferred orientation. The film annealed at 350°C showed the coexistence of CIASe and InSe phases. The average crystallite size increases linearly with annealing temperature, reaching a maximum value for 350°C. The films show a direct allowed band gap which increases from 1.59 to 1.78 eV with annealing temperature. We have also found that the electrical resistivity of films is controlled by the carrier concentration rather than by their mobility.

Preparation of CuInSe_2 thin films by paste coating

Precursor pastes were obtained by milling Cu-In alloys and Se powders. CulnSe2 thin films were successfully prepared by precursor layers, which were coated using these pastes, and were annealed in a H2 atmosphere. The pastes were tested by laser particle diameter analyzer, simultaneous thermogravimetric and differential thermal analysis instruments （TG-DTA）, and X-ray diffractometry （XRD）. Selenized films were characterized by XRD, scanning electron microscopy （SEM）, and energy dispersive spectroscopy （EDS）. The results indicate that chalcopyrite CuInSe2 is formed at 180℃ and the crystallinity of this phase is improved as the temperature rises. All the CuInSe2 thin films, which were annealed at various temperatures, exhibit the preferred orientation along the （112） plane. The compression of precursor layers before selenization step is one of the most essential factors for the preparation of perfect CuInSe2 thin films.

First-principles study on the alkali chalcogenide secondary compounds in Cu(In,Ga)Se_2 and Cu_2ZnSn(S,Se)_4 thin film solar cells

The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.

Effects of Cu and Co Substitution on the Properties of NiZn Ferrite Thin Films

Cu- and Co-substituted NiZn ferrite thin films, Ni0.4-xZn0.6CuxFe2O4 and Ni0.5Zn0.5CoxFe2-xO4 （0≤x≤0.2）, are synthesized by sol-gel process. The crystallographic and magnetic properties of Cu- and Co-substituted NiZn ferrite thin films have been investigated. The lattice parameter decreases with Cu substitution and increases with Co substitution. The saturation magnetization decreases and the coereivity increases with the increase of Cu substitution. Moreover, the saturation magnetization gradually increases with the increase of Co substitution when x≤0.10, but decreases when x〉0.10. Meanwhile, the coereivity initially decreases with the increase of Co substitution when x≤0.10, but increases when x〉0.10.

A Comparison of Optical Properties of CuO and Cu₂O Thin Films for Solar Cell Applications

Solar energy is becoming more popular and widespread, and consequently, the materials to manufacture solar cells are becoming more limited and costly. Therefore, in order to keep solar energy affordable and available, we must research alternative materials such as copper oxides. Some benefits of copper oxides include being available in abundance, affordable, low toxicity, low bandgap, and a high absorption coefficient—all of which contribute to it being a valuable interest for the manufacturing of solar cells. In this study, CuO thin films were synthesized utilizing RF sputtering technique with deposition occurring at room temperature followed by thermal annealing between 100°C and 400°C and using different gases, oxygen (O2) (oxidizing and reactive gas) and nitrogen (N2) (inert gas), besides air. Afterwards, these thin films were evaluated for a range of wavelengths: 200 - 400 nm (UV spectrum), 400 - 700 nm (Visible spectrum), and 700 - 800 nm (IR spectrum), for both, optical transmittance and photoluminescence. In addition, the CuO results were compared to our Cu2O results from a previous study to assess their differences. In the results of this study, the CuO thin film initially had a bandgap of 2.19 eV at room temperature, and by increasing the annealing temperature to different levels, the bandgap decreased respectively. The presence of air in the chamber allowed for the highest decrease, followed by the nitrogen (N2) and the lowest decrease was observed in the presence of oxygen (O2). This was reflected in the decrease in the bandgap values from 2.19 eV (room temperature) to 2.05 eV for the films annealed at 400°C.

High Sensitivity of Porous Cu-Doped SnO2 Thin Films to Methanol

Porous Cu-doped SnO2 thin films were synthesized by the sol-gel dip-coating method for enhancing methanol sensing performance. The effect of Cu doping concentration on the SnO2 sensibility was investigated. XRD data confirm that the fabricated SnO2 films are polycrystalline with tetragonal rutile crystal structure. AFM and SEM micrographs confirmed the roughness and the porosity of SnO2 surface, respectively. UV-Vis spectrum shows that SnO2 thin films exhibit high transmittance in the visible region ~95%. The band gap (3.80 - 3.92 eV) and the optical thickness (893 - 131 nm) of prepared films were calculated from transmittance data. The sensing results demonstrate that SnO2 films have a high sensitivity and a fast response to methanol. In particular, 3% Cu-SnO2 films have a higher sensitivity (98%), faster response (10-2 s) and shorter recovery time (18 s) than other films.

Effect of Cu additive on the structure and magnetic properties of (CoPt)_(1-x)Cu_x films

CoPt thin films with various Cu contents varying from 0 vol.% to 21.5 vol.% were deposited on glass substrates by magnetron sputtering. The effects of Cu additive on the structural and magnetic properties and the ordering temperature of CoPt films were investigated in detail. The results show that the Cu in CoPt films plays an important role in promoting the ordering parameter S and reducing the ordering temperature of CoPt films. A nearly perfect （001） texture was obtained in a CoPt film doped with 15.3 vol.% Cu. Besides, the preferred orientation of the CoPt film can be changed by annealing temperature. The perpendicular growth of the CoPt film is favored at a high annealing temperature.

Diffusion barrier performance of nanoscale TaN_x thin-film

TaNx nanoscale thin-films and Cu/TaNx multilayer structures were deposited on P-type Si(100) substrates by DC reactive magnetron sputtering. The characteristics of TaNx films and thermal stabilities of Cu/TaNx/Si systems annealed at various temperatures were studied by four-point probe(FPP) sheet resistance measurement, atomic force microscopy(AFM), scanning electron microscope-energy dispersive spectrum (SEM-EDS), Alpha-Step IQ Profilers and X-ray diffraction(XRD), respectively. The results show that the surfaces of deposited TaNx thin-films are smooth. With the increasing of N2 partial pressure, the deposition rate and root-mean-square(RMS) decrease, while the content of N and sheet resistance of the TaNx thin-films increase, and the diffusion barrier properties of TaNx thin-films is improved. TaN1.09 can prevent interdiffusion between Cu and Si effectively after annealing up to 650 ℃ for 60 s. The failure of TaNx is mainly attributed to the formation of Cu3Si on TaN/Si interface, which results from Cu diffusion along the grain boundaries of polycrystalline TaN.