Study of amorphous Ta2O5 thin films by DC magnetron reactive sputtering

The dc magnetron reactive sputtering deposition of tantalum pentoxide (Ta₂O₅) thin films was investigated. By combining Schiller's criterion and Reith’s “target preoxidation” procedure, high quality Ta₂O₅ thin films were prepared at a high deposition rate of about lOOÅ;/min. The deposited films were amorphous, with a refractive index around 2.07 and a dielectric constant of 20. An optical transmit-tance of 98.6% was obtained for a 4500Â thick film. The leakage current density is 5 × 10^?9 A/cm² at an electric field strength of 1 MV/cm and its breakdown field strength is above 2 MV/cm. The temperature coefficient of capacitance for capacitors fabricated using the deposited films is approximately +230 ppm/°C. X-ray photoelectron spectroscopy shows that the films are stoichiometric tantalum pentoxide, Ta₂O₅, and exhibit good stability.     

Effect of thickness on the structural,optical and electrical properties of RF magnetron sputtered GZO thin films

Gallium-doped zinc oxide (GZO) thin films with very high conductivity and transparency were successfully deposited by RF magnetron sputtering at a substrate temperature of 400 °C. The dependence of the film properties over the thickness was investigated. X-ray diffraction (XRD) results revealed the polycrystalline nature of the films with hexagonal wurtzite structure having preferential orientation along [001] direction normal to the substrate. The lowest resistivity obtained from electrical studies was 5.4×10⁻⁴ Ω cm. The optical properties were studied using a UV–vis spectrophotometer and the average transmittance in the visible region (400–700 nm) was found to be 92%, relative to the transmittance of a soda–lime glass reference for a GZO film of thickness 495 nm and also the transparency of the films decreases in the near IR region of the spectra. The mobility of the films showed a linear dependence with crystallite size. GZO film of thickness 495 nm with the highest figure of merit indicates that the GZO film is suitable as an ideal transparent conducting oxide (TCO) material for solar cell applications.     

Optical and electrical properties of Al2O3 films containing silicon nanocrystals

Optical, electrical, and structural properties of Al₂O₃ films subjected to silicon-ion implantation and annealing were investigated by means of photoluminescence measurements, current-voltage measurements and transmission electron microscopy. Transmission electron microscopy revealed that silicon nanocrystals were epitaxially formed in ϑ-Al₂O₃. Visible photolum inescence was observed, for the first time, from Al₂O₃ films containing silicon nanocrystals. Observed visible photoluminescence seems to be related to quantum size effects in silicon nanocrystals as well as localized radiative recombination centers located at the interface between silicon nanocrystals and matrix, similar to porous Si and other Si nanostructures. The conduction mechanism in the samples was studied by using dc current-voltage measurements. The conduction properties depend on temperature and applied electric fields. The conduction behavior in low electric fields consists of thermally activated region dominated by the Schottky conduction and nonthermally activated region in which carrier transport is controlled by space-charge-limited currents. The conduction behavior under relatively high electric fields is almost independent of temperature and well fitted by space-charge-limited conduction.     

Thickness-dependent optoelectronic properties of CuCr0.93Mg0.07O2 thin films deposited by reactive magnetron sputtering

CuCr_0.93Mg_0.07O₂ thin films were successfully deposited by DC reactive magnetron sputtering at 1123 K from metallic targets. The influence of film thickness on the structural and optoelectronic properties of the films was investigated. X-ray diffraction (XRD) results revealed that all the films had a delafossite structure with no other phases. The optical and electrical properties were investigated by UV–VIS spectrophotometer and Hall measurement, respectively. It was found that the optoelectronic properties exhibited a thickness-dependent behavior. The optical band gap and the average transmittance of the films showed a monotonous decrease with respect to the increase in thickness. The average transmittance in the visible region decreased from 67% to 47% as the thickness increased from ~70 nm to ~280 nm. Simultaneously, the conductivity of the films fell from 1.40 S∙cm⁻¹ to 0.27 S∙cm⁻¹. According to Haacke's figure of merit (FOM), a film with a maximum FOM value of about 1.72×10⁻⁷ Ω⁻¹ can be achieved when the thickness is about 70 nm (σ≈ 1.40 S·cm⁻¹ and T_av. ≈67%).     

MoNb薄膜直流磁控溅射制备及性能研究

以Mo-10%Nb(10%为粒子数分数)合金为靶材,采用直流磁控溅射法在钠钙玻璃基板上制备了MoNb薄膜。采用台阶仪、四探针电阻仪和AFM分别测试了Mo Nb薄膜的厚度、方块电阻及表面形貌。研究了功率密度、工艺气压及衬底温度对MoNb薄膜性能及其生长特性的影响。实验结果表明:功率密度增加2倍时,MoNb薄膜的沉积速率提升1.8倍,而电阻率降低2.3倍;工艺气压增大4倍时,MoNb薄膜的沉积速率提升1.5倍,其电阻率增大13倍。同时发现:衬底温度增加了135℃时,MoNb薄膜的表面粗糙度增加0.567nm,颗粒大小增加3.36nm。     

Effect of processing parameter on structural,optical and electrical properties of photovoltaic chalcogenide nanostructured RF magnetron sputtered thin absorbing films

The aim of this work was to develop high quality of CuIn_1−xGa_xSe₂ thin absorbing films with x (Ga/In+Ga)<0.3 by sputtering without selenization process. CuIn_0.8Ga_0.2Se₂ (CIGS) thin absorbing films were deposited on soda lime glass substrate by RF magnetron sputtering using single quaternary chalcogenide (CIGS) target. The effect of substrate temperature, sputtering power & working pressure on structural, morphological, optical and electrical properties of deposited films were studied. CIGS thin films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Energy dispersive X-ray spectroscopy (EDAX), Atomic force microscopy (AFM), UV–vis–NIR spectroscopy and four probe methods. It was observed that microstructure, surface morphology, elemental composition, transmittance as well as conductivity of thin films were strongly dependent on deposition parameters. The optimum parameters for CIGS thin films were obtained at a power 100 W, pressure 5 mT and substrate temperature 500 °C. XRD revealed that thin film deposited at above said parameters was polycrystalline in nature with larger crystallite size (32 nm) and low dislocation density (0.97×10¹⁵ lines m⁻²). The deposited film also showed preferred orientation along (112) plane. The morphology of the film depicted by FE-SEM was compact and uniform without any micro cracks and pits. The deposited film exhibited good stoichiometry (Ga/In+Ga=0.19 and In/In+Ga=0.8) with desired Cu/In+Ga ratio (0.92), which is essential for high efficiency solar cells. Transmittance of deposited film was found to be very low (1.09%). The absorption coefficient of film was ~10⁵ cm⁻¹ for high energy photon. The band gap of CIGS thin film evaluated from transmission data was found to be 1.13 eV which is optimum for solar cell application. The electrical conductivity (7.87 Ω⁻¹ cm⁻¹) of deposited CIGS thin film at optimum parameters was also high enough for practical purpose.     

直流磁控溅射制备非晶硅薄膜的研究

非晶硅薄膜（a-Si）是目前重要的光敏材料,在很多领域得到广泛应用。直流磁控溅射具有工艺简单．沉积温度低等优点,是制备薄膜的一种重要技术。采用直流磁控溅射工艺在玻璃基板上沉积薄膜,并对样品进行了退火处理。研究了沉积速率与溅射功率的关系。结果表明薄膜的沉积速率与溅射功率近似有线性关系。利用X射线衍射（XRD）对薄膜进行了分析鉴定,结果表明溅射的薄膜是非晶硅薄膜。利用扫描电子显微镜（SEM）对非晶硅薄膜的表面形貌进行了观察和分析,与X射线衍射测试的结果一致。所以．利用直流磁控溅射工艺能在常温下能快速制备出良好的非晶硅薄膜。     

直流磁控溅射制备非晶硅薄膜的研究

非晶硅薄膜(a-Si)是目前重要的光敏材料,在很多领域得到广泛应用.直流磁控溅射具有工艺简单,沉积温度低等优点,是制备薄膜的一种重要技术.采用直流磁控溅射工艺在玻璃基板上沉积薄膜,并对样品进行了退火处理.研究了沉积速率与溅射功率的关系.结果表明薄膜的沉积速率与溅射功率近似有线性关系.利用X射线衍射(XRD)对薄膜进行了分析鉴定,结果表明溅射的薄膜是非晶硅薄膜.利用扫描电子显微镜(SEM)对非晶硅薄膜的表面形貌进行了观察和分析,与X射线衍射测试的结果一致.所以,利用直流磁控溅射工艺能在常温下能快速制备出良好的非晶硅薄膜.     

Characteristics of DC magnetron sputtered ternary cobalt-nickel silicide thin films for ultra shallow junction devices

Ternary cobalt-nickel silicide thin films were synthesized by DC magnetron sputtering from an equiatomic cobalt-nickel alloy target. Grazing incidence XRD, Rutherford back scattering, high-resolution cross-sectional TEM analysis and electrical study were carried out to investigate the formation of silicide, stoichiometry, film thickness, depth profile and sheet resistance of as-deposited and post-deposition annealed films. The ternary silicide layer thickness was calculated from RBS simulated data, which was found to vary 20-43 nm for as-deposited and different vacuum annealed films. A minimum value of sheet resistance 2.73 Ω/sq corresponding to a resistivity of ∼8.4 μΩ-cm was obtained for optimized deposition and annealing conditions.     

Electrical breakdown in very thin Al2O3 films

Electrical breakdown in very thin A1₂O₃ films of thickness less than 100 Å and sandwiched between Al and Au metal electrodes has been studied experimentally. Recovery of high resistance of the oxide insulator film has been observed (after breakdown) on the application of either a reverse voltage or a high current pulse or just by resting the junction for a few hours after the removal of the applied external voltage. An explanation for the effect is suggested. The breakdown field is found to depend on the insulator thickness, the temperature and the nature of the electrode metals. On the basis of experimental results the mechanisms for electrical break down at room temperatures and above, in very thin Al₂O₃ films, can be attributed to electronic modified thermal breakdown.     

Effect of 100 MeV O7+ ion beam irradiation on radio frequency reactive magnetron sputtered ZnO thin films

Zinc oxide (ZnO) thin films were deposited on sapphire substrates at room temperature by radio frequency (RF) magnetron sputtering. These films were irradiated with 100 MeV O⁷⁺ ions of the fluencies 5×10¹³ ions/cm² at room temperature (RT) and at liquid nitrogen temperature (LNT). Profilometer studies showed that the roughness of pristine and LNT irradiated ZnO thin films were higher than that of the RT irradiated ZnO thin film. The glancing angle X-ray diffraction analysis reveals a reduced intensity and increased full width at half maximum (FWHM) of the (002) diffraction peak in the case of LNT irradiated film indicating disorder. However, the intensity and FWHM of the (002) diffraction peak in the case of RT irradiated ZnO thin films are comparable to those of the pristine film. UV–visible transmission spectra show that the percentage of transmission and band gap energy are different for RT and LNT irradiated films. While the pristine ZnO thin film exhibits two emissions—a broad emission at 403 nm and a sharp emission at 472 nm in its photoluminescence spectrum; the emission at 472 nm was absent for the irradiated films. The atomic concentrations of zinc and oxygen during the irradiation process were obtained using auger electron spectroscopy.     

Study of electrical and optical properties of CNx thin films deposited by reactive magnetron sputtering

The study concerns the CN_x thin films deposited by Low Pressure Hot Target Reactive Magnetron Sputtering (LP-HTRMS). The thin film resistance changes with relative humidity (RH) and optical properties have been studied in the range of 300-653 K. The temperature coefficients of resistivity changes were −2.5%/K at 300 K and −0.5%/K at 500 K. The activation energy of conductivity E_ρ was found to be 0.21 eV in the case of unannealed sample and 0.44 eV when the sample was annealed at 653 K. The CN_x thin films fastness to light was tested in the range of 200-2500 nm by measuring their transmittance. The calculations of absorption carrying out with Tauc formula proved the dominance of indirect optical transitions with Eg energy of 1.04 eV and direct transitions of Eg 2.05 eV. The UV radiation was fully absorbed and light transmission was ca. 90% in the range from visible radiation to far infrared of 1000-2500 nm. The CN_x thin films showed the high resistance sensitivity to RH changes. At T = 300 K resistance changed from 882 M Ω for 36% RH to 386 k Ω for 85% RH. The CN_x thin films susceptibility to humidity was observed in case of both DC and AC current (100 Hz to 10 kHz) measurements. The Si₃N₄ or SiC buffer adhesive layer was incorporated between CN_x film and substrate and its influence on CN_x electrical properties was observed.     

衬底温度对磁控溅射生长HMGZO薄膜特性的影响

为适应高效Si基薄膜太阳电池对宽光谱透明导电 薄膜的需求,采用磁控溅射技术 生长了不同衬 底温度氢化作用下Ga和Mg共掺杂ZnO(HMGZO)透明导电氧化物(TCO)薄膜。研究了不同衬底温 度(200～280 ℃)对HMGZO薄膜 结晶特性及光电特性的影响。实验结果表明,制备的HMGZO薄膜均为具有六角纤锌矿结构的 多晶薄膜,呈 现(002)晶面择优生长。随着衬底温度的升高,薄膜中Mg含量逐渐增加,并且薄膜表面新型 锥状结构趋于 致密和均匀化。在各元素含量和结晶质量的共同影响下,其电阻率随着温度的升高从6．70×10－4 Ω·cm增加至7．63×10－4 Ω·cm。所有薄膜在可 见光区域(380～800 nm)的透过率均在80%以上,由于载流子共振吸收的作用,近红外区域的 透过率有所下降。MgO扩展带隙的作用和 Burstein-Moss(BM)效应的影响共同促进了薄膜光学带隙E_g展 宽,使得E_g达到了3.75 eV。当衬底温度为280 ℃ 时,薄膜方块电阻为4.91 Ω/sq,电阻率为7.63×10－4 Ω·cm,光电性能指数ΦTC值达0.022 Ω－1。     

磁控溅射法制备氧化钒薄膜的研究

主要介绍了红外探测器的分类、发展,及基于氧化钒薄膜的热探测器的优势;采用直流磁控溅射法在相对较低温度220℃下制备出电阻温度系数(TCR)为-1.9%/℃的VOx薄膜.通过XRD、AFM、红外透过测试方法对薄膜的形貌、组分及其红外吸收性能进行分析,结果表明该VOx薄膜非常适合用作非制冷红外探测器热敏材料.与传统的工艺相比,由于该薄膜淀积过程无需高温退火,在后期的红外焦平面制作过程中,可以较好地保护红外焦平面阵列的CMOS电路.     

Structural and electrical properties of radio frequency magnetron sputtered tantalum oxide films: Influence of post-deposition annealing

The as-deposited and annealed radio frequency reactive magnetron sputtered tantalum oxide (Ta₂O₅) films were characterized by studying the chemical binding configuration, structural and electrical properties. X-ray photoelectron spectroscopy and X-ray diffraction analysis of the films elucidate that the film annealed at 673 K was stoichiometric with orthorhombic β-phase Ta₂O₅. The dielectric constant values of the tantalum oxide capacitors with the sandwich structure of Al/Ta₂O₅/Si were in the range from 14 to 26 depending on the post-deposition annealing temperature. The leakage current density was <20 nA cm^?2 at the gate bias voltage of 0.04 MV/cm for the annealed films. The electrical conduction mechanism observed in the films was Poole–Frenkel.     

Structure and optical properties of thin Al2O3 films deposited by the reactive ion-plasma sputtering method on GaAs (100) substrates

Structural analysis and optical spectroscopy are used to study the properties of ultrathin Al₂O₃ films deposited in an ion-plasma sputtering installation. It is possible to demonstrate that the technological method used to deposit the films can yield amorphous, smooth, pore-free, and almost homogeneous films in which crystals of the α phase of aluminum oxide Al₂O₃ nucleate. The films transmit light extremely well in the IR (infrared), visible, and UV spectral ranges and are of potential importance for the development on their basis of antireflection coatings for mirrors of high-power semiconductor lasers based on III–V compounds.     

直流磁控溅射法制备非晶态氧化钒薄膜光学特性研究

研究了直流反应磁控溅射工艺中衬底温度对氧化钒(V2O5)薄膜性能的影响,利用X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、X射线衍射(XRD)和紫外-可见光分光光度计(UV1700)分别对薄膜进行了表征.实验结果表明,除了组分和晶态,薄膜的形貌和光学性能受衬底温度的影响很大.随着衬底温度的升高,膜表面变得粗糙,膜厚减小.光学特性测试表明,当衬底温度从160℃升高到320 ℃,光学带隙从2.39 eV下降到2.18 eV.     

Electrical properties of zinc oxide sputtered thin films

ZnO thin films were deposited on silicon substrate by rf magnetron sputtering from metallic zinc target. The electrical properties of ZnO are currently being studied. In this work, measurements of the ac conductivity properties of ZnO sandwich structures with silver and platinum electrodes are reported. The frequency dependence of both the ac conductivity and dielectric constant of thin films of ZnO have been investigated in the frequency range 5 kHz-13 MHz. It is shown that the total ac conductivity σ(ω), obeys the equation σ(ω)=Aω^S where s is an index which increases with frequency and decreases with temperature. It appears that for ZnO films, the conduction mechanism is thermally activated and both the overlap large polaron tunnelling and the correlated barrier-hopping of charge carrier over localized states fit the experimental data. The dielectric constant, ε_r, lies in the range 8-9 at room temperature and is independent of the frequency in the dielectric thin films.     

Effect of tantalum doping on the structural and optical properties of RF magnetron sputtered indium oxide thin films

Tantalum doped indium oxide films are prepared by RF magnetron sputtering technique and the films are annealed in air at 300 °C. The effect of Ta doping on the structural, morphological, and optical properties of the annealed films are studied using techniques like X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), EDX analysis, micro-Raman, UV–visible and photoluminescence spectroscopy and electrical measurements. The XRD patterns present a cubic bixbyite structure for all the films with preferred orientation along the (222) plane. The lattice constant estimation presents a reduction in lattice size with Ta doping. The W–H plot shows a tensile strain for all the films and also indicates the presence of strain induced broadening of the XRD peaks. The Raman spectra present all the characteristic modes of In₂O₃ cubic bixbyite phase. FESEM and AFM images show the uniform and dense distribution of smaller grains in the films. All the films show high transmittance (above 85%) in the 400–900 nm region. Electrical measurement shows a systematic increase of carrier concentration and electrical conductivity with increase in Ta doping concentration. Band gap energy increases with increase in Ta doping concentration. All the films show intense PL emission in the UV region.     

Preparation and gas-sensing properties of α-Fe2O3 thin films

Haematite (α-Fe₂O₃) thin films are prepared by two different chemical vapor deposition (CVD) processes: the atmospheric pressure CVD (APCVD) and the plasma enhanced CVD (PECVD). The films are analyzed by x-ray diffraction and scanning electron microscopy; their gas-sensing properties are also investigated. Experimental results show that APCVD α-Fe₂O₃ films are highly sensitive and selective to smoke while PECVD films are highly sensitive and selective to alcohol. A certain amount of quadrivalent metal in the films has an effect on their sensitivity and selectivity to gases. It is found that the films will “break down” under certain conditions.