Substrate temperature-dependent physical properties of nanocrystalline zirconium titanate thin films

Nanocrystalline zirconium titanate thin films were deposited by direct current magnetron reactive sputtering on to glass substrates at room temperature and at different substrate temperatures of 423, 473, 523, and 573 K under high vacuum conditions. The deposited films have been characterized to study the physical properties of the films as a function of substrate temperature. Though the film exhibited amorphous characteristics at room temperature the higher temperatures resulted in the evolution of crystallites in the films. The crystallinity increased with temperature from 423 K onwards and the film deposited at 523 K exhibited a high crystallite size of 22 nm. The SEM images of the films revealed the improvement in the crystallinity from 423 to 523 K with dense columnar structure normal to the substrate. Further higher treatment deteriorated the film properties. The films showed a good transmittance of above 80%. A high optical transmittance of 91% and a high packing density of 96% have been observed for the film deposited at 523 K. The thickness of the films remained consistent at ~230 nm (±6 nm). It is noticed that an increase in the substrate temperature enhanced the structural, optical, and electrical properties of the films up to 523 K.     

Thermal stability of lead sulfide nanocrystalline films

Thermally stable nanocrystalline films of lead sulfide PbS were prepared using the chemical deposition method. The thickness of the films measured by interferometry was approximately equal to 100 nm, and the average particle size determined from the broadening of the X-ray diffraction reflections was approximately 80 nm. X-ray diffraction analysis revealed that annealing of the film at a temperature of 350°C in air results in the formation of a protective oxide sulfate phase of the composition PbO · PbSO₄ on the surface of the film. It was established that the oxide sulfate phase prevents a further oxidation of the film and serves as an inhibitor of the growth of PbS nanoparticles upon heating up to a temperature of 500°C. The factors responsible for the high thermal stability of the sizes of nanoparticles and the optical properties of the PbS nanocrystalline film were discussed.     

Characterization of polycrystalline SnO2 films deposited by DC sputtering technique with potential for technological applications

Polycrystalline SnO₂ films with different thicknesses were successfully deposited on glass substrate at room temperature using a DC sputtering technique. As-grown films showed the formation of an amorphous SnO₂ phase, whereas the thermal annealed samples showed the formation of a SnO₂ rutile-type structure. The structural study showed that the crystallinity of the annealed films was improved as a function of film thickness. Scanning electron microscopy images of the annealed films unveiled the formation of cracked surfaces along with columnar growth, irrespective of the depositon time. Raman spectroscopy measurements evidenced the presence of modes related to a surface disorder,a progressive strain reduction and a crystallinity improvement. UV–vis data analysis indicates a reduction in the band gap energy with films thickness due to presence of strain states as confirmed by theoretical calcuations. It was observed that the strained states in the films affected the sensing response to a methane gas flow with a better sensitivity for the thinner film.     

Si field emitter arrays coated with thin ferroelectric films

This paper demonstrates novel approach on Si field emitter arrays (FEAs) coated with thin ferroelectric films for vacuum microelectronic applications, which exhibit enhanced electron emission behaviors. The films were deposited using sol–gel and sputtering process, respectively. In sol–gel approach, the emission behavior is highly correlated to the crystallinity of (Ba,Sr)TiO₃ (BST) layer. The interfacial reaction between Si and BST film would deteriorate the crystallinity of the films, and in turn impede the electron emission from silicon tips. The film thickness and the dopants also affect the emission behaviors significantly. In sputtering process, the nitrogen-incorporated SrTiO₃ (STO) films are deposited with eliminated interfacial due to relatively lower processing temperature. The enhanced emission characteristics are highly correlated with nitrogen-incorporation and film thickness. These encouraging results have offered great promise for the application of ferroelectric films in field emission devices.     

Tunability of optical constants of Se-Ge-Ag thin films based on change in resistivity with temperature for solar cells

Thin films of semiconductor Se₈₀Ge_20-xAg_x (x = 0, 3, 6, 9, 12 and 15 at.%) were deposited by the thermal evaporation technology. Through optical and electrical characterization, the influence of the Ag ratio on the photoelectric parameters of Se–Ge thin film was studied. The X-ray diffraction pattern showed the amorphous nature of the deposited films as well as the polycrystalline state when the films were annealed at the maximum crystallization temperature (415 K), which was determined by the first derivative of the resistivity curve with respect to temperature. The crystallization kinetics of the film was extracted from the electrical analysis by measuring the change in resistivity with temperature. The electrical results of the thin film showed three regions; namely, amorphous, extended (crystalline) and hopping. In the extended and hopping states, the activation energy and pre-exponential factors were calculated. The optical constants, extinction coefficient and refractive index were calculated using the transmittance and reflectance of the grown Se₈₀Ge_20-xAg_x films. The energy gaps of the films were estimated in the strong absorption regions. The changes in the bandgap energy of the film by thermal annealing can help to produce materials with acceptable band gaps for use as absorber layers in solar cell applications. Also, the results provide microscopic insights and studies on the structure, electr-othermal and optical properties of Ag metal-doped GeSe as a back contact of solar cells.     

Characterization of CdTe Films Deposited at Various Bath Temperatures and Concentrations Using Electrophoretic Deposition

CdTe film was deposited using the electrophoretic deposition technique onto an ITO glass at various bath temperatures. Four batch film compositions were used by mixing 1 to 4 wt% concentration of CdTe powder with 10 mL of a solution of methanol and toluene. X-ray Diffraction analysis showed that the films exhibited polycrystalline nature of zinc-blende structure with the (111) orientation as the most prominent peak. From the Atomic Force Microscopy, the thickness and surface roughness of the CdTe film increased with the increase of CdTe concentration. The optical energy band gap of film decreased with the increase of CdTe concentration, and with the increase of isothermal bath temperature. The film thickness increased with respect to the increase of CdTe concentration and bath temperature, and following, the numerical expression for the film thickness with respect to these two variables has been established.     

Preparation of diamond like carbon thin films above room temperature and their properties

Diamond like carbon (DLC) thin films were deposited on p-type silicon (p-Si), quartz and ITO substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at different substrate temperatures (RT ∼ 300 °C). Argon (Ar: 200 sccm) was used as carrier gas while acetylene (C₂H₂: 20 sccm) and nitrogen (N: 5 sccm) were used as plasma source. Analytical methods such as X-ray photoelectron spectroscopy (XPS), FT-IR and UV–visible spectroscopy were employed to investigate the structural and optical properties of the DLC thin films respectively. FT-IR spectra show the structural modification of the DLC thin films with substrate temperatures showing the distinct peak around 3350 cm^− 1 wave number; which may corresponds to the sp² C–H bond. Tauc optical gap and film thickness both decreased with increasing substrate temperature. The peaks of XPS core level C 1 s spectra of the DLC thin films shifted towards lower binding energy with substrate temperature. We also got the small photoconductivity action of the film deposited at 300 °C on ITO substrate.     

薄膜厚度对Al掺杂ZnO薄膜性能的影响

采用直流磁控溅射技术,以氧化锌铝陶瓷靶为靶材,在玻璃衬底上制备了ZnO：Al（ZAO）薄膜样品。在其他参数不变的情况下,由不同溅射时间得到了不同厚度的薄膜,研究了薄膜的结构性质、电学和光学性质随薄膜厚度的变化关系。实验结果表明：在薄膜厚度为500 nm时,ZAO薄膜具有最优化的光电性能,电阻率为1.68×10-3Ω.cm,可见光区平均透射率为90.3%。     

Boron doped amorphous carbon thin films grown by r.f. PECVD under different partial pressure

Boron doped hydrogenated amorphous carbon (a-C) thin films have been deposited by r.f.-plasma CVD with a frequency of 13.56 MHz at room temperature using pure methane as a precursor of carbon source mixed with hydrogen (H₂) as a carrier gas. The films were prepared by varying the r.f. power, different flow rates of CH₄, and partial pressure of mixed gas (CH₄/H₂) using solid boron as a target. The thickness, structural, bonding and optical properties of the as-deposited films were studied by Alpha step surface profiler, Raman, FT-IR, XPS and UV–visible spectroscopy. It was found that changing the deposition pressure in presence of solid boron dopant in the r.f. PECVD process has a profound effect on the properties of the deposited films, as evidenced from their Raman scattering and optical results. The grown p-C: B films were found very smooth and thickness in the range of 240 to 360 nm for 1 h deposition. Films deposited at lower pressure appear brownish color whereas those deposited at higher pressure appear pale yellowish. The as-deposited film is found to be dominated by sp² rather than sp³, which might be due to the formation of small crystallites. The optical band gap is found to be reduced from 2.601.58 eV as the partial pressure of CH₄/H₂ gas is reduced.     

Chemical solution deposition of pure and Gd-doped ceria thin films: Structural,morphological and optical properties

High quality smooth, uniform and crack-free ceria and gadolinium doped ceria (GDC) thin films were prepared on Si and Si/YSZ substrates by chemical solution deposition. The thermal behavior of Gd-Ce-O precursor was investigated by TG-DSC measurements. The phase purity and structure of deposited films were evaluated using X-ray diffraction (XRD) analysis and Raman spectroscopy. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed for the estimation of surface morphological features. Oxidation state of Ce ions in fabricated films was analyzed by X-ray photoelectron spectroscopy (XPS). Optical properties were evaluated by diffuse reflectance UV–vis spectrometry. Thickness of the films can be controlled by applying a certain number of spin coating cycles. A linear relation between the thickness of the films and the number of deposited layers was observed. The single-layer thickness was determined to be approximately 20 nm. The influence of annealing temperature and Gd content on the film structure, morphology and optical properties was studied and discussed. The dependence of an optical band gap as a function of grain size was demonstrated.     

聚醚醚酮薄膜的性能研究

采用挤出流延法制备了一系列聚醚醚酮（PEEK）薄膜，通过拉力机、差示扫描量热仪、紫外分光光度计、透光率雾度仪等对PEEK薄膜的基本性质、光学性能、力学性能进行了研究。结果表明，PEEK薄膜的透光率随结晶度的升高而降低；拉伸速率对拉伸强度、断裂伸长率的影响不大，拉伸速率快，屈服强度明显提高；拉伸强度随流延辊速度的增加而提高；双向拉伸的方法可使薄膜拉伸强度达到203 MPa；增加薄膜厚度、提高结晶度的方法可以提高薄膜的抗紫外性能。     

Effect of Ar:N2 flow rate on morphology,optical and electrical properties of CCTO thin films deposited by RF magnetron sputtering

Calcium copper titanate (CCTO) thin films were deposited on indium tin oxide (ITO) substrates using radio frequency (RF) magnetron sputtering, at selected Ar:N₂ flow rates (1:1, 1:2, 1:4, and 1:6 sccm) at ambient temperature. The effect of Ar:N₂ flow rate on the morphology, optical and electrical properties of the CCTO thin films were investigated using FESEM, XRD, AFM, Hall effect measurement, and UV–Vis spectroscopy. It was confirmed by XRD analysis that the thin films were produced is CCTO with cubic crystal structure. As the flow rate of Ar:N₂ increased up to 1:6 sccm, the thin film thickness reduced from 87 nm to 35 nm while the crystallite size of CCTO thin film decreased from 27 nm to 20 nm. Consequently, the surface roughness of thin film was halved from 8.74 nm to 4.02 nm. In addition, the CCTO thin films deposited at the highest Ar:N₂ flow rate studied, at 1:6 sccm; are having the highest sheet resistivity (13.27 Ω/sq) and the largest optical energy bandgap (3.68 eV). The results articulate that Ar:N₂ flow rate was one of the important process parameters in RF magnetron sputtering that could affect the morphology, electrical properties and optical properties of CCTO thin films.     

TiO2 optical coating layers for self-cleaning applications

TiO₂ films deposited by various coating techniques were investigated for self-cleaning applications. The optical coating layers of TiO₂ films prepared from a sol–gel precursor were deposited on glass substrates using spin coating, dip coating and screen printing techniques. Effects of film deposition techniques on crystal structure, microstructure, thickness, photocatalytic activity, hydrophilicity and optical properties of the films were investigated using XRD, AFM, SEM, surface profilometer, UV–vis spectrophotometer and contact angle measurement. Dip coating the TiO₂ optical film two and three times resulted in superhydrophilic surfaces. Increasing number of dipping times was found to increase the photocatalytic activity.     

Biaxial elastic modulus of very thin diamond-like carbon (DLC) films

The biaxial elastic modulus of very thin diamond-like carbon (DLC) films was measured by the recently suggested free overhang method. The DLC films of thickness ranging from 33 to 1100 nm were deposited on Si wafers by radio frequency plasma-assisted chemical vapor deposition (r.f.-PACVD) or by the filtered vacuum arc (FVA) process. Because the substrate was partially removed to obtain sinusoidal free overhang of the DLC film, this method has an advantage over other methods in that the measured value is not affected by the mechanical properties of the substrate. This advantage is more significant for a very thin film deposited on a substrate with a large difference in mechanical properties. The measured biaxial elastic moduli were reasonable values as can be judged from the plane strain modulus of thick films measured by nanoindentation. The biaxial elastic modulus of the film deposited by r.f.-PACVD was 90±3 GPa and that of the film deposited by FVA process was 600±50 GPa. While the biaxial elastic modulus of the film deposited by FVA is independent of the film thickness, the film deposited by r.f.-PACVD exhibited decreased elastic modulus with decreasing film thickness when the film is thinner than 500 nm. Although the reason for the different behavior could not be clarified at the present state, differences in structural evolution during the initial stage of film growth seem to be the reason.     

A comprehensive study on the effects of alternative sulphur precursor on the material properties of chemical bath deposited CdS thin films

Chemical bath deposition (CBD) method was used to deposit CdS thin films on soda-lime glass substrates by using n-methylthiourea (NTU) as an alternative sulphur source and were compared to typical thiourea (TU) precursor. The sulphur source concentration was varied from 0.01 M to 0.1 M and the impact on the microstructural, surface morphology, optical and electrical properties of the grown films were studied. Increasing n-methylthiourea concentration in the precursor yielded thinner films that are less than 100 nm thickness, surface morphology with average surface roughness of 6.4 nm, larger granular structure, wider band gap at 2.3 eV–2.6 eV range. Raman spectroscopy revealed Raman peak at 303 cm-1. In contrast, an increase in thiourea concentration resulted in thinner amorphous films, less distinct granular structure, narrower energy band gap from 2.3 eV to 2.4 eV and a resonance Raman peak at 302 cm-1. CdS thin film deposited from n-methylthiourea precursor at higher precursor concentration of 0.1 M showed better electrical properties such as lower resistivity and higher carrier mobility compared to the thin film deposited from typical thiourea precursor.     

Mechanical,thermal, and electrical conducting properties of CNTs/bio‐degradable polymer thin films

The objective of this study is to increase mechanical, thermal, and electrical properties of plasticizer free thermoplastic bio polymer, BIOPLAST GS 2189 (BP), a blend of poly lactic acid (PLA) and potato starch. This polymer is highly suitable for sheet molding, film processing; blown film extrusion and injection molding and fully biodegradable. Structural, mechanical, thermal, and electrical properties of these films were manipulated by reinforcement of multiwalled carbon nanotubes (CNTs) in BP. Thin films of various (1–5 wt %) percentages of CNTs/BP were prepared by using a high‐speed spin coating technique. These as‐prepared films are ～60–100 µm in thickness. The thickness measurements of these films were carried out using micrometry and optical microscopy. The maximum tensile strength (200%) and modulus (150%) was observed for 4 wt % loading of CNTs in BP as compared with the neat BP thin film. The X‐ray diffraction results show that the addition of CNTs in BP increases the crystallinity of BP. Electrical conductivity of this film also increased by 48% as compared with the neat BP polymer films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of crystallinity on surface morphology and light transmittance of poly(vinylidene fluoride‐co‐hexafluoropropylene) thin film

Homopolymer of vinylidene fluoride and its copolymers containing hexafluoropropylene (HFP) were prepared from free radical solution polymerizations and spin‐coated on the glass slides to fabricate thin film with a thickness of ～ 1 μm. It was found that the surface morphology of fluorinated thin films was strongly dependent on the crystallinity of polymers. In addition, the surface morphology was the most important factor to determine the optical transmittance of glass coated with the fluoropolymer thin film. As decreasing the crystallinity of the polymer by introducing HFP with a bulky CF₃ moiety, the surface of thin film became flattened and the transmittance of visible light was increased by reducing scattering. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Facile solution deposition of ZnIn2S4 nanosheet films on FTO substrates for photoelectric application

In this paper, ZnIn(2)S(4) perpendicular nanosheet films have been directly deposited on FTO substrates by a facile hydrothermal method and investigated as the electrode materials for solar cells. The crystal structure, morphology, and optical properties of the obtained ZnIn(2)S(4) films were characterized by measurements such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrum (EDS), X-ray photoelectron spectrum (XPS) and UV-vis spectra. The results revealed a uniform perpendicular ZnIn(2)S(4) film with thickness of 4 μm and with an average nanosheet thickness of about 30 nm on FTO substrate, along with the band gap of 2.35 eV. The reaction conditions influencing the formation of ZnIn(2)S(4) films, such as the substrate treatment and reaction time were investigated. A possible mechanism for the formation of ZnIn(2)S(4) films on FTO substrates under hydrothermal conditions has been proposed. Furthermore, after heat treatment, the ZnIn(2)S(4) film electrode exhibited a photoelectrical conversion efficiency of 0.23% in FTO/ZnIn(2)S(4)/polysulfide/Au liquid-junction solar cell under AM 1.5 (100 mW cm(-2)).     

Ultrathin carbon film from carbonization of spin-cast polyacrylonitrile film

Here we present ultrathin carbon films derived from polyacrylonitrile precursor film. Subsequent carbonization was investigated to examine the optical and electrical properties of resulting carbon films. The precursor PAN solution was carefully prepared and heated in order to have thin and uniform PAN film, and X-ray reflectivity of the precursor film and the carbon film shows uniformity. X-ray diffraction pattern of the carbon film indicated that the obtained carbon films possess low crystallinity. It was also found that the thickness for ultrathin carbon film from PAN layer showed counterbalanced optical and electrical performance in the range of experiment.     

铁酸铋功能陶瓷薄膜的液相自组装制备

利用自组装单层膜技术,以三氯十八烷基硅烷(octadecyl trichlorosilane,OTS)为模板,以硝酸铋和硝酸铁为原料,在玻璃基片上成功制备了铁酸铋(BiFeO3)晶态薄膜。采用接触角仪测量了紫外光照射后OTS单层膜的亲水性。通过X射线衍射、扫描电镜和能谱仪等表征了BiFeO3薄膜的物相、表面形貌及微观结构。结果表明:紫外光照射使OTS单层膜由原来的强疏水性转变为良好的亲水性,说明OTS自组装膜层表面已被羟基化。在70℃沉积8h并经600℃退火2h制备的BiFeO3薄膜结晶良好,薄膜样品的表面平整,厚度较为均匀,薄膜厚度约为100nm。