Temperature dependent electrical transport studies of self-aligned ZnO nanorods/Si heterostructures deposited by sputtering
TL;DR: In this article, self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques and the average diameter, height, and density of NRs were found 48'nm, 750'nm and 1.26'×'1010'cm−2, respectively.
Abstract: Self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques. The NRs are uniformly grown on 2-inch wafer along [0001] direction. Single-crystalline wurtzite structure of ZnO NRs was confirmed by X-ray diffraction. The average diameter, height, and density of NRs are found 48 nm, 750 nm, and 1.26 × 1010 cm−2, respectively. The current-voltages (I-V) characteristics of ZnO NRs/Si heterojunction (HJ) were studied in the temperature range of 120–300 K and it shows a rectifying behavior. Barrier height (ϕB) and ideality factor (η) were estimated from thermionic emission model and found to be highly temperature dependent in nature. Richardson constant (A*) was evaluated using Richardson plot of ln(Io/T2) versus q/kT plot by linear fitting in two temperature range 120–180 K and 210–300 K. Large deviation in Richardson constant from its theoretical value of n-Si indicates the presence of barrier inhomogeneities at HJ. Double Gaussian distribution of barrier height with thermionic...
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TL;DR: In this article, the growth of vertically c-axis oriented, highly aligned and separated ZnO nanorods at substrate temperatures of 700-750°C is explained by considering that the growth above 600°C, takes place in the 'desorption regime' in which, the surface diffusion length decreases exponentially with temperature.
47 citations
TL;DR: In this paper, the residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 109 to 11.28 x 109 dyne/cm2 with compressive in nature.
Abstract: ZnO thick Stress relaxed films were deposited by reactive magnetron sputtering on 2”-wafer of SiO2/Si at room temperature. The residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 109 to 11.28 x 109 dyne/cm2 with compressive in nature. Sputter pressure changes the deposition rates, which strongly affects the residual stress and surface morphologies of ZnO films. The crystalline wurtzite structure of ZnO films were confirmed by X-ray diffraction and a shift in (0002) diffraction peak of ZnO towards lower 2θ angle was observed with increasing the compressive stress in the films. The band gap of ZnO films shows a red shift from ∼3.275 eV to ∼3.23 eV as compressive stress is increased, unlike the stress for III-nitride materials. A relationship between stress and band gap of ZnO was derived and proposed. The stress-free growth of piezoelectric films is very important for functional devices applications.
46 citations
01 Jan 2019
TL;DR: An overview of β-Ga2O3-based UV photodetectors as well as their status and promises are presented in this article, where a comparison in terms of device performance between the two technologies for UV detection is made.
Abstract: An overview of β-Ga2O3-based UV photodetectors (PD) as well as their status and promises are presented in this chapter. UV detectors and their applications are highlighted in the introduction followed by a brief discussion on β-Ga2O3 and its many potentials and challenges. The figures of merit for a PD are touched upon, especially from the point of view of UV detection. β-Ga2O3 UV detector configurations such as metal-semiconductor-metal (MSM) and Schottky diodes are discussed, and their recent advances and state-of-the-art results are presented in parallel. A comparison in terms of device performance between β-Ga2O3 and the competing III-nitride technology for UV detection is also highlighted. Finally, the future outlook and challenges associated with this emerging UV technology are summarized.
42 citations
TL;DR: In this paper, a H2 sensing mechanism based on the change in physical dimension of channel is proposed to explain the fast response and recovery times of ZnO NRs/Si/ZnONRs sensors.
Abstract: Uniformly distributed and defect-free vertically aligned ZnO nanorods (NRs) with high aspect ratio are deposited on Si by sputtering technique. X-ray diffraction along with transmission electron microscopy studies confirmed the single crystalline wurtzite structure of ZnO. Absence of wide band emission in photoluminescence spectra showed defect-free growth of ZnO NRs which was further conformed by diamagnetic behavior of the NRs. H2 sensing mechanism based on the change in physical dimension of channel is proposed to explain the fast response (∼21.6 s) and recovery times (∼27 s) of ZnO NRs/Si/ZnO NRs sensors. Proposed H2 sensor operates at low temperature (∼70 °C) unlike the existing high temperature (>150 °C) sensors.
41 citations
TL;DR: In this article, a systematic investigation of temperature dependent currentvoltage (I-V) characteristics of Pd/ZnO Schottky barrier diodes in the 30-300-k temperature range was performed.
41 citations
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TL;DR: The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.
Abstract: One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.
32 citations
TL;DR: In this paper, a heavily compensated and intrinsic ZnO layer (i-ZnO) doped with both Mg and Na was deposited on the nominally undoped ZnOs, which show a natural n-type behavior.
19 citations
TL;DR: In this paper, thin films of ZnO were grown on p-type Si (100) substrates by thermal oxidation and structural characterization of the thin films was carried out by X-ray diffraction and scanning electron microscopy (SEM).
Abstract: Thin films of ZnO were grown on p-type Si (100) substrates by thermal oxidation. The in situ growth of the metallic Zn films were thermally oxidized at different temperatures ranging from $300 to 500 ^0 C$ to yield ZnO thin films. The structural characterization of the thin films was carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The X-ray diffraction measurements show that the films deposited at $500 ^0 C$ had better crystalline quality than the rest. The electrical transport properties of the ZnO/Si heterojunction were investigated by current–voltage (I–V) and capacitance–voltage (C–V) measurements. The heterojunction exhibited a barrier height, which is consistent with the energy difference between the work functions of Si and ZnO. Complex impedance spectroscopy measurements at temperatures ranging from $50 to 125 ^0 C$ were performed on these heterojunctions.
15 citations
TL;DR: In this article, the structural properties of ZnO nanorods were characterized by X-ray di raction spectrometer and morphological characteristics were analyzed by scanning electron microscopy, respectively.
Abstract: Vertically well-aligned ZnO nanorods arrays were synthesized on sapphire substrates by chemical bath deposition Those sapphire substrates were seeded to control the density and orientation of ZnO nanorods using sol gel method Well-aligned and uniformly distributed ZnO nanorods in a large scale were obtained with strongly (002) preferential orientation The structural properties were characterized by X-ray di raction spectrometer and morphological characteristics were analyzed by scanning electron microscopy, respectively The ZnO nanorods are obvious hexangular wurtzite structure and preferentially oriented along the c-axis (002) and growth vertically to the substrates The optical properties were further thoroughly studied What is more, the in uences of the strain between substrate and ZnO nanorods due to thickness of the ZnO seed-layer on the characteristics and optical properties of ZnO were also analyzed
10 citations
TL;DR: In this article, X-ray diffraction measurements revealed the peaks corresponding to the ZnO crystal directions of (002), (101) and (200) confirmed by the Joint Committee on Powder Diffraction Standards (JCPDS) files, indicating the polycrystalline nature of the films.
Abstract: p-ZnO thin films were grown by electrochemical deposition (ECD) technique on n-Si substrate in order to form the p-ZnO/n-Si heterojunction. Hall measurement and hot probe techniques were used to determine the conductivity type of the ECD grown ZnO thin film. X-ray diffraction measurements revealed the peaks corresponding to the ZnO crystal directions of (002), (101) and (200) confirmed by the Joint Committee on Powder Diffraction Standards (JCPDS) files, indicating the polycrystalline nature of the films. The electrical characterization of p-ZnO/n-Si heterojunction was carried out in the temperature range of 80-300 K. The ideality factor and barrier height of the structure exhibited a variation between 2.49 to 5.36 and between 0.574 and 0.173 eV for this temperature ranges, respectively. The variation with temperature observed on the electrical parameters of the p-ZnO/n-Si heterojunction was explained by the introduction of a spatial distribution of barrier heights due to barrier height in homogeneities that prevail at the p-ZnO/n-Si heterojunction interface.
Key words: ZnO thin films, p-n heterojunction, electrodeposition.
8 citations