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In the current work, thin film (∼55 nm) of n-type Ga2O3 (n-Ga2O3) is deposited on silicon (p-Si) substrate by using radio-frequency (RF) sputtering technique with systematic substrate temperature variations (room temperature to 700 °C). The structural, optical properties and chemical states of elements of the deposited films are observed to depend significantly on the deposition temperatures. The chemical composition and oxidation states, optical properties, defect states and structural quality of the deposited films are investigated in detail by employing x-ray photoelectron spectroscopy, energy dispersive x-ray, spectroscopic ellipsometry, Raman, photoluminescence and atomic force microscopy images. X-ray diffraction result reveals a polycrystalline nature of monoclinic β -phase of Ga2O3 with (403) dominant plane. The work functions are calculated from the ultraviolet photo-electron spectroscopy for all the deposited films and Ga2O3/Si heterojunction properties are investigated by using currentâ€"voltage (I â€" V) and capacitanceâ€"voltage (C â€" V) measurements. Among all the fabricated heterojunctions, 600 °C deposited Ga2O3 film exhibits superior performance in terms of energy bandgap, work function, refractive index, barrier height, rectification ratio and effective carrier concentrations. The current transport mechanism is analysed using the appropriate energy band diagram of Ga2O3 and Si. Therefore, the study suggests that 600 °C deposition temperatures is the optimum temperature for developing a high quality Ga2O3 thin film on Si by using RF sputtering technique and corresponding Ga2O3 thin film/Si heterojunction can be a potential candidate for developing several electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The current work investigates the impact of annealing temperature on the optoelectronic properties of SnO2 thin films grown by chemical bath deposition (CBD) method. The as-grown SnO2 films, on p-Si substrate, are annealed at 200 °C and 400 °C for 10 min in Ar ambient for investigating the impact of such annealing on the performance of SnO2/p-Si heterojunction solar cells. The growth of a uniform SnO2 film on Si surface has been confirmed from SEM studies and the chemical composition and optical properties of the as-grown and annealed films are investigated in detail by employing XRD and ellipsometric measurements. Absorption coefficient of the samples is observed to vary in the range of 24 × 105 – 60 × 105/m, at its band gap (3.0 eV). The current–voltage characteristics under both dark and illuminated conditions suggest superior voltaic performance of the 200 °C annealed SnO2 film. The short-circuit current density, open-circuit voltage and fill-factor are obtained to be 0.45 mA/cm2, 5.41 mA/cm2 and 0.4 V, 0.34 V and 13%, 8% respectively for as-grown and 200 °C annealed samples. The maximum power conservation efficiency (η) of 4.9% is obtained for the 200 °C annealed sample. Thus, the study indicates the potential of CBD-grown SnO2 film for photovoltaic applications. [ABSTRACT FROM AUTHOR]

In the current work, CuO thin films (~ 110 nm) are grown by employing chemical bath deposition (CBD) method on Si substrate for fabricating the p-CuO/n-Si heterojunction photodetectors. The as-grown films are annealed at 250, 550 and 850 °C for 10 min in Ar ambient for tuning optoelectronic properties of the as-grown CuO thin films. Comparative study on systematic annealing of the film within 250-550 °C indicates a morphological change of the as-grown CuO film to nano-fiber type with its chemical composition remaining unchanged. A variation of refractive index and dielectric constant in the range of 2.65-2.93 and 7.2-9.7, and a change of absorption coefficient and bandgap from 1.33 × 105 to 6.06 × 105 cm− 1 and 1.5 to 2.16 eV have been observed. The current-voltage characteristics both in dark and illuminated conditions suggest that the annealing of CuO film at 550 °C provides the best performance in terms of photo-to-dark current ratio and photoresponsivity. A respective enhancement of 5.07 and 10% for the photo-to-dark ratio and photoresponsivity has been observed for the 550 °C annealed sample. [ABSTRACT FROM AUTHOR]

In this paper, a high-quality crystalline thin film (~10 nm) of titanium dioxide (TiO2-II) phase is grown on p-GaAs (100) substrate by employing the vapor--liquid--solid method. The formation of crystalline TiO2-II films is confirmed by X-ray diffraction study. A very small rms surface roughness of ~1 nm has been measured from atomic force microscopy. The capacitance--voltage characteristics of Al/TiO2-II/GaAs metal--oxide--semiconductor (MOS) capacitor indicate the growth of excellent thin film of TiO2-II phase with high effective dielectric constant of 28, 35, 65, and 14 for the as-grown and 600 °C, 625 °C, and 650 °C annealed samples, respectively. An effective oxide thickness of ~0.7 nm, a negligible hysteresis of 10 mV, very small frequency dispersion of 3.5%, and a reduced gate leakage current of ~10-13 A/μm² at +2 V are achieved due to annealing in the temperature range of 600 °C-625 °C. Thus, this paper provides a cost-effective novel alternative technique to grow high-quality TiO2-II films on GaAs substrate which may be used as the reliable high-k gate dielectrics on III-V semiconductor-based MOS devices and circuits. [ABSTRACT FROM AUTHOR]

In this work, the high pressure phase of titanium dioxide (TiO2‐II) film is grown with vapor‐liquid‐solid (VLS) method on <100>‐GaAs substrate by utilizing the natural process‐induced‐strain, originating from the thermo‐elastic mismatch between TiO2 and GaAs in VLS process. The mismatches in thermal expansion coefficient and elastic constant of TiO2 and GaAs are Δα≈55% and ΔY≈170% which incorporate a substantial amount of stress (≈GPa) during cooling from the growth temperature (500 °C). SEM imaging suggests the formation of a continuous film and cross‐sectional TEM image confirmed its high crystalline quality. XRD peaks at 2θ = 31.300 and 58.670 confirm the formation of [111] and [212]‐planes of TiO2‐II phase and its chemical states are analyzed from X‐ray photoelectron spectroscopy (XPS) measurements. The bandgap of TiO2‐II phase is estimated to be 2.88 eV from cathodoluminescence study for the first time which agrees satisfactorily with the theoretical predictions reported. The current work deals with the formation of most stable high pressure phase of titanium dioxide, the TiO2‐II film with narrow bandgap (≈2.88 eV), on GaAs substrate by employing VLS method. Such novel approach does not require any external means to create high pressure ambience; rather utilizes the process‐induced strain originated due to inherent thermo‐elastic mismatch between TiO2 and GaAs. [ABSTRACT FROM AUTHOR]

In this work, the authors report a comparative study on the physical and electrical properties of n-ZnO nanowires (NWs)/p-Si and n-ZnO NWs/p-CuO film heterojunctions by employing chemical bath deposition method. Solar energy conversion efficiency of the n-ZnO NWs/p-CuO and n-ZnO NWs/p-Si heterojunctions is obtained to be 3.92% and 0.008%, respectively, under 100 mW/cm 2 input incident power. Thus, the n-ZnO NWs/p-CuO heterojunctions exhibit superior photovoltaic performance in comparison to the n-ZnO NWs/p-Si system. [ABSTRACT FROM AUTHOR]

Thin film of p-type cupric oxide ( p -CuO) is grown on silicon (n-Si) substrate by using chemical bath deposition (CBD) technique and a precise control of thickness from 60 nm to 178 nm has been achieved. The structural properties and stoichiometric composition of the grown films are observed to depend significantly on the growth time. The chemical composition, optical properties, and structural quality are investigated in detail by employing XRD, ellipsometric measurements and SEM images. Also, the elemental composition and the oxidation states of Cu and O in the grown samples have been studied in detail by XPS measurements. Thin film of 110 nm thicknesses exhibited the best performance in terms of crystal quality, refractive index, dielectric constant, band-gap, and optical properties. The study suggests synthesis route for developing high quality CuO thin film using CBD method for electronic and optical applications. [ABSTRACT FROM AUTHOR]

In this work, the CuO nano-powder has been synthesized by employing chemical bath deposition technique for its subsequent use to grow ultrathin film (20 nm) of p-CuO on n-Si substrate for the fabrication of p-CuO/n-Si hetero-junction diodes. The thin CuO film has been grown by employing vapour-liquid-solid method. The crystalline structure and chemical phase of the film are characterized by employing field-emission scanning electron microscopy and X-ray diffraction studies. Chemical stoichiometry of the film has been confirmed by using energy dispersive X-ray spectroscopy. The potential for photovoltaic applications of such films is investigated by measuring the junction current-voltage characteristics and by extracting the relevant parameters such as open circuit photo-generated voltage, short circuit current density, fill-factor and energy conversion efficiency. [ABSTRACT FROM AUTHOR]

• Growth of CuO film and ZnO nanowires by employing CBD method. • Potential of ZnO nanowires for improving power conversion efficiency. • Improvement of photovoltaic parametrices of p-CuO/n-ZnO NWs heterojunction. • Achievement of a significantly high solar energy conversion efficiency of 4.19%. P-type cupric oxide (p-CuO) and p-type cupric-oxide/n-type zinc oxide nanowires (p-CuO/n-ZnO NWs) heterojunction diodes were fabricated by employing chemical bath deposition technique on n-silicon (n-Si) substrate. The work demonstrates the potential of zinc oxide nanowires as window layer owing to its wide and direct band gap for metal oxide based solar cells. Optical and electronic properties of the CuO film and ZnO nanowires including refractive index, absorption coefficient and band gaps were investigated by using spectroscopic ellipsometric analysis. Impact of nanowire morphology, chemical composition and crystallite structures on optical and photovoltaic performance of p-CuO/n-Si and p-CuO/n-ZnO NWs were investigated. Absorption coefficient in the near UV–visible range was observed to improve significantly by incorporating n-ZnO nanowires which was desired for the solar cell applications. The comparative photovoltaic performance showed improvements of both the short-circuit current density (J sc) and open circuit voltage (V oc), due to reduced interface recombination and enhanced absorption for the increased surface-to-volume ratio of ZnO nanowires in the p-CuO/n-ZnO NWs heterojunction. Photovoltaic performance with J sc , V oc and power conversion efficiency of 11.1 mA/cm2, 1.1 V and 4.19% was obtained. Therefore, the work emphasizes importance of using the combination of n-ZnO nanowires and p-CuO film as the wide- and low- band gap materials for improving performance of the future low-cost solar cell with superior efficiency. [ABSTRACT FROM AUTHOR]

In the current work, a single crystalline β-Gallium Oxide (Ga 2 O 3) thin film (~15 nm) is grown on Si-substrate by employing catalyst-modified vapor-liquid-solid (VLS) method. The FESEM and AFM images indicate the formation of a continuous film with small surface roughness. XRD measurement confirms the formation of a highly crystalline < 1 ¯ 11 >-plane of β-phase of Ga 2 O 3. The chemical states and optical properties of such films are analyzed by X-ray photoelectron spectroscopy (XPS) and Spectroscopic ellipsometry (SE). The energy bandgap, refractive index and extinction coefficient of the grown β-Ga 2 O 3 film are obtained to be 4.78 eV, 1.84 and 0.10, respectively. The vacancies/defect states are studied from Photoluminescence (PL) spectra where the major PL-peaks corroborate with the transitional energy values obtained from SE measurement. Therefore, the study suggests that the VLS method, amongst the state-of-the-art growth techniques, is capable of growing high-quality single crystalline β-Ga 2 O 3 thin film in a relatively simple and cost-effective approach. Image 1061 • Growth of β-Ga 2 O 3 film is reported, for the first time, by employing VLS technique. • The Au catalyst is modified to provide ambient condition for rapid growth of the film. • Single crystalline film (~15 nm) is achieved by adopting such catalyst modified method. [ABSTRACT FROM AUTHOR]