Influence of thermal annealing on electrical and optical properties of indium tin oxide thin films

Transparent conducting indium tin oxide (ITO) thin films with the thickness of 300 nm were deposited on quartz substrates via electron beam evaporation, and five of them post-annealed in air atmosphere for 10 min at five selected temperature points from 200 °C to 600 °C, respectively. An UV–vis spectrophotometer and Hall measurement system were adopted to characterize the ITO thin films. Influence of thermal annealing in air atmosphere on electrical and optical properties was investigated in detail. The sheet resistance reached the minimum of 6.67 Ω/sq after annealed at 300 °C. It increased dramatically at even higher annealing temperature. The mean transmittance over the range from 400 nm to 800 nm reached the maximum of 89.03% after annealed at 400 °C, and the figure of merit reached the maximum of 17.79 (Unit: 10⁻³ Ω⁻¹) under the same annealing condition. With the annealing temperature increased from 400 °C to 600 °C, the variations of transmittance were negligible, but the figure of merit decreased significantly due to the deterioration of electrical conductivity. With increasing the annealing temperature, the absorption edge shifted towards longer wavelength. It could be explained on the basis of Burstein–Moss shift. The values of optical band gap varied in the range of 3.866–4.392 eV.     

Effect of low energy proton beam irradiation on structural and electrical properties of ZnO:Al thin films

In this study, we report the structural modification and change in electrical behaviour of aluminium doped zinc oxide by low energy (100 keV) proton irradiation. Aluminium doped zinc oxide films were deposited using DC magnetron sputtering and then annealed for a short duration at 600 °C before irradiation. Structural and defect studies of the films carried out using XRD and Raman spectroscopy. It suggests that the crystalline ordering increases at higher fluences due to annealing of defects in the film. The increase in crystallinity at higher fluences decreases the grain boundary scattering and causes low resistivity. There is no significant change in carrier concentration after the irradiation, however the mobility and resistivity of the Al doped ZnO films change with proton irradiated fluences. The development of defect due to irradiation has been confirmed through Raman spectroscopic studies. The increase in activation energy of particles has been suggested by low energy proton irradiations at higher fluences in the annealed Al doped ZnO thin films. The uniform particle distribution increases with fluences of the irradiation that may be helpful for spintronics and sensor device technology.     

The effect of Mg and Al co-doping on the structural and photoelectric properties of ZnO thin film

Mg–Al co-doped ZnO thin films were prepared via radio-frequency reactive magnetron sputtering technique. X-ray diffraction investigation showed all the thin films with different Mg:Al ratio had hexagonal wurtzite structure. All the thin films showed (100) preferential orientation of ZnO. When Al concentration was kept constant but Mg concentration was increased, the grain size decreased at first and then increased. When Mg:Al ratio was 3:1, the grain size reached a maximum. Ultraviolet–visible spectra showed the thin films had a high average transmittance of 80% in the visible range. The optical band gaps of the thin films were obtained as follows: 3.31, 3.32, and 3.37 eV, corresponding to the Mg:Al ratio of 0:1, 1:1, and 3:1, respectively. Photoluminescence spectroscopy showed all the thin films had four main peaks located at 386, 410, 463, and 499 nm. The origin of blue peak is oxygen vacancy. When Mg concentration was kept constant but Al concentration was increased, I–V curve presented that for both of the heterojunctions the rectifying behavior was formed. The conductivity of Mg:Al=1:1 thin film is higher than that of Mg:Al=1:0 thin film. After illumination, light I–V curve deviated from rectifying character.     

Effect of Co doping on structural, optical, electrical and thermal properties of nanostructured ZnO thin films

Nanocrystalline Zn1-x CoxO(where x varies from 0 to 0.04 in steps of 0.01) thin films were deposited onto glass substrate by the spray pyrolysis technique at a substrate temperature of 350 ℃. The X-ray diffraction patterns confirm the formation of hexagonal wurtzite structure. The crystal grain size of these films was found to be in the range of 11–36 nm. The scanning electron micrographs show a highly crystalline nanostructure with different morphologies including rope-like morphology for undoped ZnO and nanowalls and semispherical morphology for Co-doped Zn O. The transmittance increases with increasing Co doping. The optical absorption edge is observed in the transmittance spectra from 530 to 692 nm, which is due to the Co2C absorption bands corresponding to intraionic d–d shifts. The direct and indirect optical band gap energies decrease from 3.05 to 2.75 eV and 3.18 to 3.00 eV, respectively for 4 mol% Co doping. The electrical conductivity increases with increasing both the Co doping and temperature, indicating the semiconducting nature of these films. The temperature dependence thermal electromotive force measurement indicates that both undoped and Co-doped ZnO thin films show p-type semiconducting behavior near room temperature. This behavior dies out beyond 313 K and they become n-type semiconductors.     

Influence of deposition rate on the structural,optical and electrical properties of electron beam evaporated SnO2 thin films for transparent conducting electrode applications

The role of deposition rate in the structural,optical and electrical properties of SnO2 thin films deposited by electron beam evaporation method is investigated by varying the deposition powers viz.50,75,and 100 W.The structural characterization of the films is done by X-ray diffraction (XRD) technique.The surface morphology of the films is studied by scanning electron microscopy (SEM).Rutherford back scattering (RBS) measurements revealed the thickness of the films ranging from 200 nm to 400 and also a change in the concentration of oxygen vacancies which is found to be the maximum in the film deposited at the lowest deposition rate.Optical absorption spectrum is recorded using the UV-V is spectroscopy and the films are found to be transparent in nature.A shift in the absorption edge is observed and is attributed to a different level of allowed energy states in conduction band minimum.The Hall effect and electrical measurements show a variation in the carrier concentrations,mobility and resistivity of the films.In order to explore a better compromise in electrical and optical properties for transparent electrode applications,skin depths calculations are also done to find the optimized values of carrier concentration and mobility.     

Effect of seed layers (Al,Ti) on optical and morphology of Fe-doped ZnO thin film nanowires grown on Si substrate via electron beam evaporation

The effects of Al and Ti seed layers were studied for undoped and Fe-doped ZnO thin films deposited on n-type Si substrates by electron beam (e-beam) evaporation. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The films grown on seed layers showed wurtzite hexagonal crystal nanorod and nanowire structures. A higher angle phase shift was observed in the doped thin films compared to the pristine ZnO films. Microstructural studies confirmed the growth of nanorods and nanowires with average widths of ~32 nm and ~8–29 nm, respectively. The nanostructures were denser and more crystalline on the Al seed layer than on the Ti seed layer for the doped thin films. However, in the undoped thin films, a more crystalline nature was observed on the Ti seeded layer than the Al seeded layer.     

Study on the structural, electrical and optical properties of Al-F co-doped ZnO thin films prepared by RF magnetron sputtering

Al and F co-doped ZnO(ZnO:(Al,F)) thin films on glass substrates are prepared by the RF magnetron sputtering with different F doping contents.The structural,electrical and optical properties of the deposited films are sensitive to the F doping content.The X-ray analysis shows that the films are c-axis orientated along the(002) plane with the grain size ranging from 9 nm to 13 nm.Micrographs obtained by the scanning electron microscope(SEM) show a uniform surface.The best films obtained have a resistivity of 2.16×10-3Ω·cm,while the high optical transmission is 92.0% at the F content of 2.46 wt.%.     

Al薄膜对(002)ZnO/Al/Si结构基片中ZnO薄膜特性影响的实验研究

采用射频磁控溅射法沉积制备了(002)ZnO/A l/Si复合结构。研究了Al薄膜对(002) ZnO/Al/Si复合结构的声表面波器件(SAWD)基片性能影响以及当ZnO 薄膜厚度一定时的Al膜最佳厚度。采用X射线衍射(XRD)对Al和ZnO薄膜进行了结构表征 ,采用 扫描电镜(SEM)对ZnO薄膜进行表面形貌表征,并从薄膜生长机理角度进行了分析。结果 表明,加Al薄膜有利于ZnO薄膜按(002)择优取向生长,并且ZnO 薄膜的结晶性能提高;与(002)ZnO/Si结构基片相比,当Al薄膜 厚为100nm时,(002)ZnO/Al/Si结构中ZnO薄 膜的机电耦合系数提高 了65%。     

Structural, electrical and optical properties of ZnO thin films deposited by sol-gel method

Thin films of intrinsic and Al-doped ZnO were prepared by the sol-gel technique associated with spin coating onto glass substrates. Zinc acetate dehydrate, ethanol and monoethanolamine were used as a starting material, solvent and stabiliser, respectively. Structural, electrical and optical characterizations of the films have been carried out. All films are polycrystalline with a hexagonal wurtzite structure with a preferential orientation according to the direction 〈0 0 2〉. The four-points technique was used to characterize thin films electrically. All films exhibit a transmittance above 80-90% along the visible range up to 650 nm and a sharp absorption onset about 375 nm corresponding to the fundamental absorption edge 3.3 eV. Intense UV photoluminescence is observed for undoped and 1% Al-doped ZnO films.     

Influence of pH on structural,optical and electrical properties of solution processed Cu2ZnSnS4 thin film absorbers

Cu₂ZnSnS₄ (CZTS) films were obtained by the dip-coating method. The effect of different pH values 4.0, 4.5, and 5.0 on the structural, morphological, optical and electrical properties of samples was investigated by XRD, SEM, UV–vis and Hall Effect measurements. The XRD spectra showed that the characteristic peak intensity of CZTS semiconductor increased with increasing pH value of the precursor solution. It was also observed that increased pH values resulted in a significant reduction in the amount of impurity phases of the films. The UV–vis studies revealed a significant increase in the optical absorption of thin films in the visible region as the pH value of the solution was increased. The band gap of the samples shifted from 2.0 to 1.38 eV by increasing the pH value. The electrical resistivity of the films was found to vary from 2.8×10⁻² to 3.1 Ω cm, depending on its pH value.     

金属有机物化学气相淀积法生长的Si掺杂GaN薄膜的应力，结构与电学特性研究

The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metaiorganic chemical vapor deposition （MOCVD） are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.     

Stress, structural and electrical properties of Si-doped GaN film grown by MOCVD

The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.     

Carbon ions irradiation induced modifications in structural and electrical resistivity characteristics of ZrN thin films

Zirconium nitride (ZrN) thin films are irradiated with 800 keV energetic carbon (C) ions in a 5UDH-Pelletron accelerator and the ions irradiation induced effects are investigated. The films are irradiated at various C ions fluences, ranging from 10¹³ to 10¹⁵ ions/cm². The scanning electron microscopy study of the films indicates the development of zirconium (Zr) nanoparticles at ions irradiated region. X-ray diffraction (XRD) patterns of C ions irradiated films also show the formation of (100) and (002) oriented nanocrystalline metallic Zr phases. The irradiated films spectra depict a shift in ZrN peaks towards higher 2θ values, exhibiting that C ions bombardment induces compressive stress in the irradiated films. The appearance of C related peaks in Fourier transform infrared (FTIR) spectra confirms the incorporation of C atoms into ZrN film. Compressive stress has been calculated from the IR peak shift which indicates that higher ion dose (≥5×10¹⁴ ions/cm²) produce lower compressive stress relative to the lower ions fluences. Effect of ion dose on the film resistivity is also reported.     

Comparative study between electrical, optical and structural properties of annealed heavily carbon doped GaAs

Heavily C-doped GaAs epilayers have been grown by atmospheric pressure metalorganic vapor phase epitaxy with hole concentration ranging from 2×10¹⁹ to 1.6×10²⁰ cm⁻³. In order to study the stability of C acceptors over this range, the films have been annealed at 810 °C for 10 min under two mixture gas AsH₃+H₂ or only N₂. Annealing of the layers resulted in a decrease in carrier concentration, carrier mobility and lattice mismatch with undoped GaAs. The lattice matching conditions of C-doped GaAs layers were systematically investigated by using X-ray high-resolution diffraction space mapping. The comparison between electrical and structural before and after annealing of layers properties indicates that the simultaneous decrease of carrier concentrations, Hall mobility and mismatch is probably related to an increase of compensation. Basing on a theoretical calculation of mobility as a function of hole concentration and Vegard's law, we estimate that the compensation comes from the formation of (C-C)⁺_[100] interstitial couples. This fact does not exclude definitively the possibility of the formation of other species such as H-C_As especially for hole concentration lower than 5×10¹⁹ cm⁻³. An annealing under AsH₃+H₂ ameliorates the crystalline properties contrarily to an annealing under N₂. The optical properties have been investigated using Raman spectroscopy. Two main Raman features are observed before and after annealing of the layers: the longitudinal-optic (LO) phonon mode and the coupled plasmon-LO phonon (LOPC). As for as grown layers, the intensity ratio I_LOPC/I_LO between the intensity of LOPC peak and the LO peak increases by increasing the hole concentration. This ratio is about 1 after an annealing of layers under AsH₃+H₂. An unusual change of I_LOPC/I_LO ratio is observed in samples annealed under N₂. Indeed, for high doping (∼10²⁰ cm⁻³) the ratio I_LOPC/I_LO<1 and for relatively low doping (∼2×10¹⁹ cm⁻³) the ratio I_LOPC/I_LO>1. This behaviour is probably related to the high sensibility of Raman measurement not only to the hole concentration change but also to the surface quality.     

Morphology,optical and AC electrical properties of nanostructure thin film of bromo indium phthalocyanine

Sandwich devices of bromo indium phthalocyanine (BrlnPc) thin films with aluminium electrodes were deposited on polyborosilicate substrate, using electron beam gun evaporation technique at room temperature. The AC electrical properties of nanostructure thin films (Al/BrInPc/Al) were examined in the temperature range of 303–393 K and frequency (f) between 10² and 10⁵ Hz. Structural and optical behaviour of samples were investigated by scanning electron microscope (SEM) images, X-ray diffraction (XRD) micrograph and optical absorption. Capacitance increase with increasing temperature for frequencies <10³ Hz and is almost independent of temperature for the range of frequencies >10³ Hz. Dissipation factor decrease with increasing frequency to a minimum value and increased noticeably thereafter. The AC electrical properties of nanostructured thin films of our materials are in agreement with the model of Goswami and Goswami. The band theory and hopping mechanism are applicable in explaining the conduction process for the frequency range of f<10³ Hz and f>10³ Hz, respectively.     

Tailoring the structural and optical characteristics of InGaN/GaN multilayer thin films by 12 MeV Si ions irradiations

In this study, the influence of Si ions irradiations (12 MeV energetic) on structural and optical characteristics of InGaN/GaN thin film has been investigated. Irradiation was performed at different Si ions fluences in the range of 1×10¹³ to 1×10¹⁵ ions/cm². X-ray diffraction (XRD) pattern of pristine film indicates only the (0 0 2) oriented crystallites of InGaN while the irradiated films patterns showed other phases (InN and GaN) as well. Ion irradiations at different dose rates have shown no or negligible effect on grain size of InGaN except a shift in the peak position which demonstrates the development of tensile stresses. The existence of other phases in the irradiated films patterns is the indication of InGaN phase separation. Defects produced due to irradiation were also confirmed from peak shifting and appearance of new peak at 669 cm⁻¹ in Raman spectra. A decrease in optical bandgap with the increase of ion irradiation dose rate is being reported in this work.     

The structural,optical, and electrical properties of vacuum evaporated Cu-doped ZnTe polycrystalline thin films

We have studied the structural, optical, and electrical properties of thermally evaporated, Cu-doped, ZnTe thin films as a function of Cu concentration and post-deposition annealing temperature. X-ray diffraction measurements showed that the ZnTe films evaporated on room temperature substrates were characterized by an average grain size of 300Å with a (111) preferred orientation. Optical absorption measurements yielded a bandgap of 2.21 eV for undoped ZnTe. A bandgap shrinkage was observed for the Cu-doped films. The dark resistivity of the as-deposited ZnTe decreased by more than three orders of magnitude as the Cu concentration was increased from 4 to 8 at.% and decreased to less than 1 ohm-cm after annealing at 260°C. For films doped with 6–7 at.% Cu, an increase of resistivity was also observed during annealing at 150–200°C. The activation energy of the dark conductivity was measured as a function of Cu concentration and annealing temperature. Hall measurements yielded hole mobility values in the range between 0.1 and 1 cm²/V·s for both as-deposited and annealed films. Solar cells with a CdS/CdTe/ZnTe/metal structure were fabricated using Cudoped ZnTe as a back contact layer on electrodeposited CdTe. Fill factors approaching 0.75 and energy conversion efficiencies as high as 12.1% were obtained.