Impact of thickness on vacuum deposited PbSe thin films

Lead Selenide thin films were prepared by vacuum evaporation technique with different thickness ranges from 50 to 200 nm on glass substrates. The structural studies revealed that the prepared films are strongly oriented on (2 0 0) plane with rock-salt crystal structure. The various structural parameters such as grain size (D), lattice constant (a), micro strain (ε) and dislocation density (δ) were calculated. The surface morphology of the films was also analyzed. The optical absorption of the films starts with visible region and obtained energy gap of the films lies between 1.5 and 1.9 eV. The room temperature Photoluminescence spectrum shows the emission peak at visible region (380-405 nm) and the blue shift was observed with decreasing the film thickness. The electrical mobility, resistivity, carrier concentration and mean free path (L) of the free carriers of the films were studied for all the samples and compared.     

Alloying reaction in thin nickel films deposited on GaAs

The alloying reaction in a thin nickel film deposited on a GaAs substrate was investigated using microprobe Auger spectroscopy, reflection high energy electron diffraction and transmission electron diffraction. A nickel film reacts with the substrate above 200°C to form a metastable hexagonal reaction product with the composition Ni:Ga:As = 2:1:1, which is monocrystalline with the orientation relation 〈0001〉 hexagonal // 〈111〉 GaAs and 〈11$\text{2}$0〉 hexagonal // 〈110〉 GaAs. Above 400°C the metastable reaction product decomposes into NiAs and β-NiGa, both of which are also monocrystalline with the same orientation relation as the metastable reaction product. The role of nickel in GaAs contact systems is explained by the high reactivity of nickel with GaAs in the solid-solid phase.     

Studies on the photoconductivity of vacuum deposited ZnTe thin films

The present paper reports the analysis of photoconductivity of vacuum deposited zinc telluride (ZnTe) thin films as a function of substrate temperature and post-deposition annealing. Detailed analyses were first carried out to understand the effect of substrate temperature and annealing on the structure, composition, optical and electrical properties of the films. The films deposited at elevated substrate temperatures showed faster and improved photoresponse. Post-deposition annealing was found to further enhance the photoresponse of the films. Attempts have been made to explain the improvement in the photoresponse on the basis of structural and compositional changes, taking place in the films, due to the substrate temperature and annealing.     

Thermal strain in indium thin films deposited on GaAs substrates

Thermal strains in indium thin films deposited on GaAs substrates, which were introduced into the films upon cooling from 293 to 25 K, were measured using the conventional X-ray diffraction technique. Since the thermal expansion coefficients and the elastic constants of indium have strong dependences on the crystal orientation, we studied intensively the crystal orientation dependence of the strains perpendicular to the film surface. The strains measured for films with 60 nm thickness agreed well with those calculated based on a biaxial strain model using the difference in thermal expansions between the indium and the GaAs. The present strain analysis indicated that the anisotropy in the thermal expansion of indium is the prinary cause of different strains measured in grains with various crystal orientations. For the thicker films the strains were observed to deviate from the theoretical values owing to strain relaxation upon cooling.     

Fabrication and characterization of vacuum deposited fluorescein thin films

Simple vacuum evaporation technique for deposition of dyes on various solid surfaces has been developed. The method is compatible with conventional solvent-free nanofabrication processing enabling fabrication of nanoscale optoelectronic devices. Thin films of fluorescein were deposited on glass, fluorine-tin-oxide (FTO) coated glass with and without atomically layer deposited (ALD) nanocrystalline 20 nm thick anatase TiO₂ coating. Surface topology, absorption and emission spectra of the films depend on their thickness and the material of supporting substrate. On a smooth glass surface the dye initially forms islands before merging into a uniform layer after 5 to 10 monolayers. On FTO covered glass the absorption spectra are similar to fluorescein solution in ethanol. Absorption spectra on ALD-TiO₂ is red shifted compared to the film deposited on bare FTO. The corresponding emission spectra at λ = 458 nm excitation show various thickness and substrate dependent features, while the emission of films deposited on TiO₂ is quenched due to the effective electron transfer to the semiconductor conduction band.     

Transparent conducting ZnO thin films deposited by vacuum arc plasma evaporation

A high rate deposition of co-doped ZnO:Ga,F and ZnO-In₂O₃ multicomponent oxide thin films on large area substrates has been attained by a vacuum arc plasma evaporation method using oxide fragments as a low-cost source material. Highly transparent and conductive ZnO:Ga,F and ZnO-In₂O₃ thin films were prepared on low temperature substrates at a deposition rate of approximately 375 nm/min with a cathode plasma power of 10 kW. A resistivity of 4.5×10⁻⁴ Ω cm was obtained in ZnO:Ga,F films deposited at 100 °C using ZnO fragments co-doped with 1 wt.% ZnF₂ and 1 wt.% Ga₂O₃ as the source material. In addition, the stability in acid solution of ZnO films was improved by co-doping. It was found that the Zn/(In+Zn) atomic ratio in the deposited ZnO-In₂O₃ thin films was approximately the same as that in the fragments used. The ZnO-In₂O₃ thin films with a Zn/(In+Zn) atomic ratio of approximately 10-30 at.% deposited on substrates at 100 °C exhibited an amorphous and smooth surface as well as a low resistivity of 3-4×10⁻⁴ Ω cm.     

Investigation of the some physical properties of Ge-doped ZnO thin films deposited by thermionic vacuum arc technique

We exhibit the first nano-crystalline Ge–ZnO thin films deposited on glass and PET substrates by a thermionic vacuum arc technique. The effect of Ge doping on the structural, morphological and optical properties of ZnO:Ge films were investigated. An X-ray diffraction (XRD), atomic force microscopy, field emission scanning electron microscopy (FESEM) and UV–Vis spectrophotometer were used for the analysis. XRD patterns show the polycrystalline structure of the films in the range of 20°–80°. The roughness value for the ZnO:Ge on PET substrate was increased due to agglomeration of the grains. The results are in a good agreement with the FESEM images. Using Filmetrics F20 tool, the thickness values of the deposited thin films were obtained as 60 and 80 nm on glass and PET substrates, respectively. The optical properties of the films such as transmittance, absorbance, refractive index, and reflectance were determined. The band gap values were obtained as to be 3.43 and 3.38 eV glass and PET substrates, respectively. It was found that band gap variation of ZnO is very small with Ge doping.     

Ion transport studies on vacuum deposited PbSnI4 thin films

Thin films of the material PbSnI₄ have been deposited by vacuum evaporation. The electrical conductivity, its activation energy and dielectric breakdown strength have been found to be film thickness dependent for films ≤5000 Å. Conductivity is by anionic defect motion with an activation energy of 0.320 eV and ionic transference number of 0.995 at room temperature. The ionic transport has been independently verified by an electrochemical cell potential method with the use of the material in an all thin film solid state battery of the configuration M/PbSnI₄/(AgI,Ag), (M=Sn,Pb), giving OCV values close to the thermodynamic theoretical maximum for the formation of MI₂ at the anode.     

Infrared transmission properties of germanium carbon thin films deposited by reactive RF magnetron sputtering

Germanium carbon (GeC) thin films were prepared on ZnS substrates by reactive RF magnetron sputtering in Ar and CH₄ mixtures with a Ge disc as the target. H content in the films was studied as a function of the deposition parameters and low H content GeC film was obtained. RF power had a little effect on IR absorptions, hence had a little effect on H content. IR absorption of the GeC film increased a little with the increase in partial pressure of CH₄ as well as total pressure of gas mixture. Increase in substrate temperature decomposed CH₄ and CH_x in the GeC film into C and H and H was desorbed from the film, lowering the IR absorption. However, high substrate temperature prevented CH₄ or CH_x from adsorbing onto the substrate, which decreased C content in the GeC film and increased the film's refractive index. Higher annealing temperature of the GeC film reduced H content, but high annealing temperature (500 °C) caused the graphitization of the GeC film and destroyed its continuity.     

Adhesion and vacuum forming properties of tin-zinc thin films deposited on polyester film substrate

Sn-Zn alloy thin films were deposited on a polyester (PET) film substrate by co-evaporation and evaluated their surface, tensile and adhesion properties with a vacuum forming test and pull test.Relationship between the surface roughness and elemental composition of these thin films was evaluated. The surface roughness decreased with increase of the Sn content.The tensile property was estimated by observations of micro-cracks of the thin films due to a vacuum forming test. Sn-Zn alloy thin film, whose elemental composition is 85:15 (wt%), had high vacuum forming durability.The adhesion strength between the Sn-Zn alloy thin films and PET substrate was measured with a pull test apparatus. The pull strength decreased with increase of the Sn content.     

Investigation of structural properties of ITO thin films deposited on different substrates

The influence of the substrate nature on the structure and morphology of ITO thin films grown by thermal evaporation in vacuum is investigated. The as-prepared metal films with Sn/In molar ratio of 0.1 were subsequently annealed for 2 h at 723 K in air (to obtain tin doped indium oxide), then annealed in vacuum at 523 K, followed by UV irradiation (to reduce the electrical resistivity). Irrespective of substrate nature, XRD data evidence a (222) preferential orientation in films. Substrate nature, annealing in vacuum and UV irradiation influence the structure, morphology, optical, electrical and surface wetting properties of the films' surface.     

磁控溅射沉积制备SnSe薄膜及其热电性能研究

因为晶体结构以及热电性能各向异性,硒化锡(SnSe)沿b轴方向表现出优异的热电性能,受到业内的广泛关注.但关于SnSe薄膜研究的报道较少.本研究利用磁控溅射技术,将SnSe沉积到Si/SiO2基底得到SnSe薄膜,分析了沉积温度对SnSe薄膜结构和热电性能的影响.结果显示:沉积温度升高,晶粒尺寸相应增加,薄膜的结晶质量...     

Structure of vacuum deposited SnSe films

Tin selenide (SnSe) thin films prepared on mica and glass substrates by vacuum sublimation technique and examined by scanning electron microscopy and transmission electron diffraction techniques showed epitaxial and polycrystalline nature respectively irrespective of substrate temperature. Grain size of the films deposited on glass substrate increased with increase in substrate temperature.     

Optical characterization of vacuum evaporated CdZnTe thin films deposited by a multilayer method

CdZnTe thin films of thickness 450–1400 nm have been evaporated under vacuum onto unheated glass substrates, using a multilayer method. During film deposition, the two evaporation sources, separated by two glass cylinders, were maintained at temperatures of 720 K for Zn and at 925–1200 K for CdTe, respectively. After deposition, the samples were annealed in air up to 775 K. The structural and optical properties of both as-deposited and heat-treated samples were investigated. Depending on the preparation conditions and the annealing temperature, the value of the optical band gap, E_g, of respective films varied between 1.16 and 1.63 eV. The obtained results are discussed in correlation with the structure of the films and the role of Zn atoms in CdTe films.     

On morphological, structural and electrical properties of vacuum deposited pentacene thin films

Films of different thickness (50, 100, 150 and 200 nm) were deposited by thermal evaporation in vacuum on two types of substrates glass and ITO. The deposition was performed under a pressure of 10⁻⁶ mB with a rate of 0.25 nm/s. Films surface investigations showed morphological and structural changes in function of films thickness and the nature of the substrate. Films optical transmission was analysed in the 280-1600 nm spectral range and the electrical measurements were done in low vacuum (10⁻¹:10⁻² mB) and in dark.     

Influence of sputtering atmosphere on crystallinity and crystal orientation of AlN thin films deposited on polycrystalline MoSi2 substrates

Highly oriented AlN thin films have been deposited on polycrystalline MoSi2 substrates by r.f. magnetron sputtering. The total sputtering pressure and the nitrogen concentration in the sputtering gas had a significant influence on the crystallinity and crystal orientation of the films. The film deposited at a sputtering pressure of 0.6 Pa and a nitrogen concentration of 20% indicated high crystallinity, high c-axis orientation (=3.1°) and very low surface roughness (Ra=0.7 nm). The crystallinity, crystal orientation, composition and morphology of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. The nitrogen concentration hardly had an effect on the composition of the films; however, it had a great influence on the shape of the fine grains constituting the films. The shape of the grains drastically changed from triangular pyramids of various sizes to uniform fine grains with increasing nitrogen concentration. © 1998 Chapman & Hall     

VHF-PECVD沉积本征微晶硅薄膜氧污染研究

通过激活能测试装置测量VHF-PECVD高速沉积的本征微晶硅薄膜,并对不同沉积功率、不同沉积压强条件下沉积制备的样品的激活能进行了分析研究。结果表明:在不同功率、不同气压沉积条件下沉积的微晶硅薄膜,激活能偏低,薄膜在沉积过程中被氧杂质污染;随着沉积功率的增大和沉积气压的增大,沉积速率随着提高,样品的激活能升高,通过提高沉积功率和沉积气压可以有效的抑制氧污染。