Effect Of Hydrogen Plasma Treatment Research Articles

Effects of Hydrogen Plasma Treatment on the Electrical Behavior of Solution-Processed ZnO Thin Films.

In this study, the effect of atmospheric hydrogen plasma treatment on the in-plane conductivity of solution-processed zinc oxide (ZnO) in various environments is reported. The hydrogen-plasma-treated and untreated ZnO films exhibited ohmic behavior with room-temperature in-plane conductivity in a vacuum. When the untreated ZnO film was exposed to a dry oxygen environment, the conductivity rapidly decreased, and an oscillating current was observed. In certain cases, the thin film reversibly 'switched' between the high- and low-conductivity states. In contrast, the conductivity of the hydrogen-plasma-treated ZnO film remained nearly constant under different ambient conditions. We infer that hydrogen acts as a shallow donor, increasing the carrier concentration and generating oxygen vacancies by eliminating the surface contamination layer. Hence, atmospheric hydrogen plasma treatment could play a crucial role in stabilizing the conductivity of ZnO films.

Effect of Hydrogen Plasma Treatment on the Sensitivity of ZnO Based Electrochemical Non-Enzymatic Biosensor.

Information on vitamin C-ascorbic acid (AA)-content is important as it facilitates the provision of dietary advice and strategies for the prevention and treatment of conditions associated with AA deficiency or excess. The methods of determining AA content include chromatographic techniques, spectrophotometry, and electrochemical methods of analysis. In the present work, an electrochemical enzyme-free ascorbic acid sensor for a neutral medium has been developed. The sensor is based on zinc oxide nanowire (ZnO NW) arrays synthesized via low-temperature chemical deposition (Chemical Bath Deposition) on the surface of an ITO substrate. The sensitivity of the electrochemical enzyme-free sensor was found to be dependent on the process treatments. The AA sensitivity values measured in a neutral PBS electrolyte were found to be 73, 44, and 92 µA mM-1 cm-2 for the ZnO NW-based sensors of the pristine, air-annealed (AT), and air-annealed followed by hydrogen plasma treatment (AT+PT), respectively. The simple H-plasma treatment of ZnO nanowire arrays synthesized via low-temperature chemical deposition has been shown to be an effective process step to produce an enzyme-free sensor for biological molecules in a neutral electrolyte for applications in health care and biomedical safety.

Effect of hydrogen plasma treatment of nanodiamond on the tribological properties of polytetrafluoroethylene-based nanocomposite coating

ABSTRACT Carbon atom recombination and etching of the surface of nanodiamond (ND) by hydrogen plasma and their effects on the dispersion and the tribological properties of a polytetrafluoroethylene (PTFE) nanocomposite coating were investigated. The surface-modified ND samples subjected to plasma treatment were characterized using FESEM, HRTEM, Raman spectroscopy, FT-IR spectroscopy and XPS. The results showed that the plasma treatment facilitates etching and recombination of the ND surface and modifies the crystallinity of the graphitic amorphous carbon. The tribological properties of the PTFE-based nanocomposite coatings prepared with the modified ND depended on the content of sp 3 -bonded carbon on the surface and the crystallinity of the ND. Hydrogen plasma treatment caused a significant improvement in the dispersion and tribological properties of the PTFE/ND nanocomposite coating due to surface modification of the ND.

Effects of hydrogen plasma treatment on the physical and chemical properties of tin oxide thin films for ambipolar thin-film transistor applications

In this study, we investigated the physical and chemical properties of H 2 plasma-treated tin oxide (SnO X ) thin films, followed by their applications in ambipolar thin-film transistors (TFTs). Finely controlled H 2 implantation was carried out using a reactive-ion-etching system at a radio frequency power of 30 W and under various exposure times. H 2 plasma treatments induced changes in the chemical structures and surface morphologies of the SnO X thin films, including a partial phase transformation of Sn and SnO to SnO 2 . The defects originating from oxygen vacancies (O Vac s) in the SnO X thin films were passivated by H via the formation of Sn–H bonds, which decreased the density of subgap states in the SnO X thin films. The H 2 plasma-treated SnO X TFTs showed considerably improved ambipolarity and electrical performance. Complementary metal–oxide–semiconductor (CMOS) logic inverters comprising H 2 -plasma-treated ambipolar SnO X TFTs exhibited a maximum gain of 34.5 V/V at a supply voltage of 10 V. The results of this study present the meaningful investigation of H 2 plasma-treated ambipolar SnO X TFTs that can be used to fabricate CMOS circuits for various applications.

Effect of Hydrogen Plasma Treatment on Atomic Layer Deposited Silicon Nitride Film

Changes in the thin film properties of SiNx deposited via atomic layer deposition using remote N2 plasma were investigated based on the frequency of adding a hydrogen (H2) plasma treatment step during the process. The deposition rate decreased from 0.36 to 0.32 A cycle−1 when compared to SiNx deposited through the conventional deposition process for a thin film that was subjected to H2 treatment processes every 10th cycle, every 5th cycle, and every single cycle of SiNx deposition compared to the deposition process without H2 plasma at a temperature of 400 °C. As the hydrogen treatment process increased beyond a 5:1 ratio, the hydrogen content in the thin film increased based on secondary ion mass spectroscopy analysis, and a change in binding energy state was shown via X-ray photoelectron spectroscopy. The thin film deposited using the hydrogen plasma treatment process at a ratio of 10:1 showed similar characteristics to the SiNx thin film deposited through the conventional atomic layer deposition process and showed excellent etch resistance without an increase in the etch rate. The step coverage characteristics were increased by 16% compared to the deposition process without a H2 plasma treatment process.

Effect of hydrogen plasma treatment on the electrical properties for SiC-based power MOSFETs

This study investigates the effects of hydrogen plasma treatment on the leakage current and capacitance characteristics of metal–insulator–semiconductor (MIS) structures on SiC substrate. The H2 plasma treatment resulted in improved breakdown voltage and reduced defect density (Nd) in an atomic-layer-deposited 30 nm-thick Al2O3 (top)/15 nm-thick SiO2 bi-layer dielectric. The breakdown voltage in Al2O3/SiO2 bi-layer dielectric after H2 plasma treatment was improved by about 6.2% (initial 47 V). The value of Nd decreased by about one order in the Al2O3/SiO2 bi-layer dielectric from 2.3 × 1011/cm2 to 3.4 × 1010/cm2 after H2 plasma treatment. Further, the interface trap density (Dit) of Al2O3/SiO2 bi-layer dielectrics was 1.4 × 1012 cm−2·eV−1, and 50% of that of the SiO2 single dielectric film.

Reversible control of the metal-insulator transition in V2O3 thin films through plasma hydrogenation

We investigate the effect of hydrogen plasma treatment on the metal-insulator transition (MIT) of epitaxial V2O3 films grown on c-Al2O3. The films were exposed to plasma at constant power for varying intervals. With increasing hydrogenation the films display a suppression of the MIT magnitude and temperature due to neutralization of structural defects and passivation of unpaired bonds by incorporation of atomic hydrogen as supported by relaxation in strain by XRD and Raman spectroscopy analysis, while stabilizing the metallic phase due to reduction in Peierls dimerization of V-V bonds. Heating to 350-400 °C the electrical characteristics of the film in the as-grown state are regained showing the possibility of reversibly controlling the MIT characteristics.

Hydrogen passivation: a proficient strategy to enhance the optical and photoelectrochemical performance of InGaN/GaN single-quantum-well nanorods

Recently, III-nitride semiconductor nanostructures, especially InGaN/GaN quantum well nanorods (NRs), have been established as a promising material of choice for nanoscale optoelectronics and photoelectrochemical (PEC) water-splitting applications. Due to the large number of surface states, III-nitride NRs suffer from low quantum efficiency. Therefore, control of the surface states is necessary to improve device performance in real-time applications. In this work, we investigated the effect of hydrogen plasma treatment on the optical properties of InGaN/GaN single-quantum-well (SQW) NRs. The low-temperature photoluminescence (PL) studies revealed that yellow and green emissions overlapped and the yellow band is more dominant in the pristine InGaN/GaN SQW NRs. However, the emission corresponding to yellow luminescence was strongly suppressed and the green emission is more intensified in hydrogenated InGaN/GaN SQW NRs. Furthermore, the time-resolved PL spectroscopy studies revealed that the carrier lifetimes of hydrogenated InGaN/GaN SQW NRs are relatively short compared to the pristine InGaN/GaN SQW, indicating the effective reduction of non-radiative centers. From the PEC measurement, the photocurrent density of hydrogenated InGaN/GaN SQW NRs in the H2SO4 solution is found to be 5 mA cm−2 at −0.48 V versus reversible hydrogen electrode, which is 3.5-fold larger than that of pristine ones. These findings shed new light on the significance of surface treatment on the optical properties and thus nanostructured photoelectrodes for PEC applications.

Study of Atmospheric-Pressure Plasma Enhanced Chemical Vapor Deposition Fabricated Indium Gallium Zinc Oxide Thin Film Transistors with In-Situ Hydrogen Plasma Treatment.

Amorphous InGaZnO (a-IGZO) Thin Film Transistors (TFTs) has been studied extensively for their perspective applications in next generation active-matrix displays such as liquid crystal displays and flat-panel displays, due to its better field-effect mobility (>10 cm²/V · S), larger Ion/Ioff ratio (>106), and better stability electrical. Hydrogen is known as shallow donors for n-type (channel) oxide semiconductors (Dong, J.J., et al. 2010. Effects of hydrogen plasma treatment on the electrical and optical properties of Zno films: Identification of hydrogen donors in ZnO. ACS Appl. Mater. Interfaces, 2, pp.1780-1784), and it is also effective passivator for traps (Tsao, S.W., et al., 2010. Hydrogen-induced improvements in electrical characteristics of a-IGZO thin-film transistors. Solid-State Electron, 54, pp.1497-1499). In this study, In-Situ hydrogen plasma is applied to deposit IGZO channel. With atmospheric-pressure PECVD (AP-PECVD), IGZO thin film can be deposited without vacuum system, large area manufacturing, and cost reducing (Chang, K.M., et al., 2011. Transparent conductive indium-doped zinc oxide films prepared by atmospheric pressure plasma jet. Thin Solid Films, 519, pp.5114-5117). The results show that with appropriate flow ratio of Ar/H₂ plasma treatment, the a-IGZO TFT device exhibits better performance with mobility (μFE) 19.7 cm²/V · S, threshold voltage (VT) 1.18 V, subthreshold swing (SS) 81 mV/decade, and Ion/Ioff ratio 5.35×107.

GaN nanowires/ p-Si interface passivation by hydrogen plasma treatment

The effect of hydrogen plasma treatment on the electrical and optical properties of GaN NWs/Si based vertical hetero structures synthesized by the method of plasma molecular beam epitaxy is studied. The effect of treatment has been carefully studied by variation of the passivation duration. Measurements of the electron beam-induced current (EBIC) technique showed the absence of potential barriers between the active parts of the diode and the contacts, which indicates the ohmic behavior of the latter. The current - voltage characteristics show that hydrogen can efficiently passivate recombination centers at the GaN NWs/Si heterointerface. It is established that the optimal passivation duration, providing improved electrical properties, is 10 minutes in the adopted passivation modes. It is shown that a longer treatment causes a deterioration in electrical properties.

Effects of hydrogen plasma treatment on the electrical performances and reliability of InGaZnO thin-film transistors

In this work, we have investigated the effects of hydrogen (H) plasma treatment on the electrical performances and reliability of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs). By optimizing the H plasma treatment time, the a-IGZO TFT with H plasma treatment time of 1 min exhibits excellent electrical performances and reliability, such as high field-effect mobility (μFE) of 26.5 cm2/V s and small threshold voltage shifts (ΔVth) value of 2.5 V and −2.3 V under positive gate bias stress (PBS) and negative gate bias stress (NBS) measurements without any passivation layers. The increased performance relies that the H plasma treatment not only could increase the carrier concentration (Ne) but also reduce the surface defects of channel layer and interface trap density of a-IGZO TFTs. The X-ray photo-electron spectroscopy measurement reveals that the H treatment passivated the oxygen vacancy (VO) defects and formed center-bonded complex states (HO or VO-H) in the a-IGZO films, which act as a shallow donor in a-IGZO films. Therefore, the high performances and excellent reliability of a-IGZO TFTs is suggesting that H is a very promising treatment for TFTs to be used for flexible thin film electronic applications.

Effect of hydrogen plasma treatment on the passivation performance of TiOx on crystalline silicon prepared by atomic layer deposition

The authors report on the effect of hydrogen plasma treatment (HPT) on the passivation performance of titanium oxide (TiOx) on crystalline silicon (c-Si) fabricated by atomic layer deposition. Recently, TiOx has gathered attention as an electron-selective contact material for silicon heterojunction (SHJ) solar cells due to its preferable work function and band lineup. Moreover, TiOx has excellent light transmission properties due to its large bandgap energy. In order to improve the power conversion efficiency of SHJ solar cells with TiOx, it is necessary to enhance the passivation performance. The effective carrier lifetime representing the passivation performance is enhanced by HPT and amounts to 407.2 μs after HPT at 200 °C for 1 min. This value is twice as high as after forming gas annealing, which is the standard method to enhance the passivation performance of TiOx/c-Si heterostructures. Nuclear reaction analysis clarifies that the hydrogen concentration (CH) at the TiOx/c-Si interface of the HPT-processed sample is higher than that of an as-deposited sample and that the peak position of the CH distribution is shifted closer to the TiOx/c-Si heterointerface after HPT. Moreover, thermal desorption spectroscopy shows that Si–H and Si–H2 hydrogen bonds increase with HPT. These results indicate that the atomic hydrogen produced by the hydrogen plasma diffuses toward the TiOx/c-Si interface and terminate the local dangling bonds, which is responsible for the improved passivation performance.

Effect of hydrogen plasma treatment on secondary electron emission properties of polycrystalline diamond films

The polycrystalline diamond films were prepared by microwave plasma chemical vapor deposition (MPCVD), and the prepared diamond films were treated with hydrogen plasma for different times. The secondary electron emission (SEE) performance of these films were studied. The film treated with plasma for 10 min has the highest SEE yield. It was found that when the films are exposed to the hydrogen plasma, the film surfaces are etched with the hydrogen plasma and the surface content of C–H components are increased with the exposure time, conversely, the oxygen content of the surfaces are gradually reduced, which leads to the higher SEE yield. When the film is continuously irradiated by the incident electron beam, the SEE yield will decrease with time, this is because the electron beam bombardment destroys the hydrogen-termination and decreases the film's surface negative electron affinity (NEA).

Hydrogen plasma treatment of β -Ga2O3: Changes in electrical properties and deep trap spectra

The effects of hydrogen plasma treatment of β-Ga2O3 grown by halide vapor phase epitaxy and doped with Si are reported. Samples subjected to H plasma exposure at 330 °C developed a wide (∼2.5 μm-thick) region near the surface, depleted of electrons at room temperature. The thickness of the layer is in reasonable agreement with the estimated hydrogen penetration depth in β-Ga2O3 based on previous deuterium profiling experiments. Admittance spectroscopy and photoinduced current transient spectroscopy measurements place the Fermi level pinning position in the H treated film near Ec-1.05 eV. Annealing at 450 °C decreased the thickness of the depletion layer to 1.3 μm at room temperature and moved the Fermi level pinning position to Ec-0.8 eV. Further annealing at 550 °C almost restored the starting shallow donor concentration and the spectra of deep traps dominated by Ec-0.8 eV and Ec-1.05 eV observed before hydrogen treatment. It is suggested that hydrogen plasma exposure produces surface damage in the near-surface region and passivates or compensates shallow donors.

Etching effects of hydrogen plasma treatment on diamond surfaces

Hydrogen plasma was employed to etch the surfaces of diamond films under various sputtering time. After hydrogen plasma treatments, the surface morphologies and phase structures of diamond films were investigated by scanning electron microscopy, atomic force microscopy, three-dimension white light interferometer, X-ray photoelectron spectroscopy and Raman spectroscopy, respectively. The results showed that the etching mainly concentrates on the crystal grains at the early stage. Many steps, pits, together with abundant subgrains, appear on the surface of the diamond crystalline. At the same time, the surface roughness decreases. At this stage, etch of sp3 phase is prior to that of sp2 phase. When the sputtering time prolongs, the sculpture of grain boundaries begin to accelerate. At this stage, the surface roughness increases and the sp2 phase is etched much faster than the sp3 phase.

Effects of Hydrogen Plasma Treatment Condition on Electrical Properties of β-Ga2O3

The effects of hydrogen or deuterium plasma treatment at 330°C on electrical properties and deep trap spectra of n-type β-Ga2O3 films grown by halide vapor phase epitaxy on native n+ substrates are reported. Under plasma treatment conditions giving rise to higher energy ions (280 eV), hydrogen penetrates into the HVPE films and fully compensates or passivates shallow donors to ∼2 μm from the surface. The Fermi level in this high-resistivity layer is pinned by electron traps near Ec-1 eV (E3 traps) also present in the starting material. Annealing at 450°C shifts the pinning position to another dominant deep trap in the starting material, the E2* traps near Ec-0.75 eV. Subsequent annealing at 550°C almost fully restores the electrical properties. By sharp contrast, plasma treatment under conditions of low energy ions (35eV) severely reduced hydrogen incorporation and only slightly increased the near-surface donor concentration. The observed differences are discussed under the assumption that hydrogen is introduced in the form of isolated acceptor interstitials with the charge transfer level near Ec-0.5 eV in the first case, but as a donor with level inside the conduction band in the second case as proposed by recent theoretical calculations.

Effects of hydrogen plasma treatment on sol-gel-derived ZnO studied by impedance spectroscopy

Effects of hydrogen plasma treatment on the electrical properties of a sol-gel-derived polycrystalline zinc oxide (ZnO) system have been studied by employing impedance spectroscopy. Complex impedance data were analyzed by employing an equivalent circuit. Hydrogen plasma treatment markedly increased the low-frequency range of constant values of the real part of complex impedance. As a result of plasma treatment, electrical conductivity was found to increase by about two orders of magnitude, with the activation energy being reduced from 0.62 eV to 0.30 eV. The dielectric constant also showed a two-fold increase following the plasma treatment.

Structure and tribological properties of plasma-treated carbide derived carbon layer

The effect of hydrogen plasma treatment on the nanocrystal structure and tribological properties of carbide derived carbon (CDC) was investigated. The CDC layer was formed on a SiC substrate using chlorine gas at 1000 °C. The plasma treatment was performed on the CDC layer via plasma-enhanced chemical vapor deposition (PECVD) and plasma exposure times of 1, 3, 5, 10 and 15 h were used. Raman spectra and transmission electron microscopy measurements revealed that the carbon layer of the 5 h-treated CDC layer consisted of nanocrystal phases; prior to the treatment, the carbon layer was mainly composed of amorphous carbon structures. Furthermore, the effect of the plasma treatment on the tribological properties of the CDC layer was investigated. The optimum friction coefficient value of 0.09 and a slightly enhanced wear rate were obtained after the 5 h plasma treatment. These results showed that the plasma treatment transformed the carbon structure of the CDC and increased the amount of sp3-bonded nanocrystal structures. As a result, the tribological properties of the CDC layer were optimized by using the plasma treatment.

Hydrogen plasma-mediated modification of the electrical transport properties of ZnO nanowire field effect transistors

We investigated the effects of hydrogen plasma treatment on the electrical transport properties of ZnO nanowire field effect transistors (FETs) with a back gate configuration. After hydrogen plasma treatment of the FET devices, the effective carrier density and mobility of the nanowire FETs increased with a threshold voltage shift toward a negative gate bias direction. This can be attributed to the desorption of oxygen molecules adsorbed on the surface of the nanowire channel, to passivation and to doping effects due to the incorporation of energetic hydrogen ions generated in plasma.

Enhanced photocatalytic performance in atomic layer deposition grown TiO2 thin films via hydrogen plasma treatment

The authors report the effect of hydrogen plasma treatment on TiO2 thin films grown by atomic layer deposition as an effective approach for modifying the photoanode materials in order to enhance their photoelectrochemical performance. Hydrogen plasma treated TiO2 thin films showed an improved absorption in the visible spectrum probably due to surface reduction. XPS analysis confirmed the formation of Ti3+ states upon plasma treatment. Hydrogen plasma treatment of TiO2 films enhanced the measured photocurrent densities by a factor of 8 (1 mA/cm2 at 0.8 V versus normal hydrogen electrode) when compared to untreated TiO2 (0.12 mA/cm2). The enhancement in photocurrent is attributed to the formation of localized electronic states in mid band-gap region, which facilitate efficient separation and transportation of photo excited charge carriers in the UV region of electromagnetic spectrum.