RF Magnetron Sputtering Method Research Articles

Deposition of ZnO thin films with different powers using RF magnetron sputtering method: Structural, electrical and optical study

Zinc Oxide thin films at room temperature with good crystallinity quality have been deposited at different Radio Frequency powers. Magnetron sputtering technique has been carried out on glass and oriented Si(100) substrates. The film structure has been characterized by X-ray Diffraction (XRD) and MicroRaman spectroscopy, which possesses a wurtzite structure with (002) preferential orientation selecting suitable conditions. Scanning electron microscope (SEM) and atomic force microscopy (AFM) have been utilized to determine the films surface morphology. The stoichiometry has been verified by Energy dispersive X-ray spectroscopy (EDX) analysis. The optical behaviors of the deposited films have been characterized by Ultraviolet Visible (UV-Vis) (optical transmittance measurements) as well as by Photoluminance characterization. Electrical properties, Current-Voltage (I-V) and Capacitance-Voltage (C-V) have been studied in details for Zinc Oxide on Silicon film that deposited at different Radio Frequency power. The high transparency, electrical behavior and smooth surface allow to use these Zinc Oxide films in photovoltaic cells and optoelectronics application.

Structural insight into nanoscale inhomogeneity of electrical properties in highly conductive polycrystalline ZnO thin films doped using methane

Recently, methane has been demonstrated as an effective n-type dopant for ZnO thin films deposited using the RF-magnetron sputtering method. It was shown that the major electrical doping effect of methane is caused by hydrogen released during methane decomposition. This work investigates the origin of the observed increase in conductivity of methane-doped ZnO films with the increase in thickness. The study is aimed at describing the nature of this thickness-dependent effect through a detailed analysis of the thickness-dependent morphology and crystalline structure. A combination of structural, electrical, and optical characterization revealed a transition from fine-grained films with a random orientation at early stages to partially (002)-textured films with columnar grains at later stages of growth. It is demonstrated that grain/sub-grain boundaries increase the electrical conductivity and that the contribution of such buried inner boundaries increases with increasing thickness. It is proposed that hydrogen diffuses along the grain and sub-grain boundaries during growth, leading to continuous doping of the buried interfaces. This hydrogen diffusion mechanism results in an apparent ‘additional doping’ of thicker films. The results provide new insights into the thickness-dependent conductivity of doped polycrystalline ZnO films mediated by hydrogen diffusion along internal interfaces.

Effects of Oxygen Defects in Zr Oxide-Based Thin Films on Oxygen Reduction Reaction in Acidic Media

The use of carbon-supported platinum as cathode catalysts of polymer electrolyte fuel cells has some problems such as high cost and low amount of resources of platinum. Therefore, we have attempted to develop substitute of platinum based on group 4 metal oxides. In the case of Zr oxide-based powder catalysts, we found that zirconium oxide-based compounds with oxygen defects and deposited carbon derived from organometallic precursors had definite activity of oxygen reduction reaction (ORR) [1][2]. However, the ORR activities of these catalysts still remain low. In order to increase the ORR activity drastically, it is necessary to clarify the catalyst design. This requires an understanding of the active sites and the electron conduction path separately, which were not separated in powder catalysts. On the other hand, Sugino et al. investigated the effect of oxygen vacancies and nitrogen doping on the active site based on first-principles calculations [3]. Defects by oxygen vacancies and nitrogen dopants were introduced into the tetragonal ZrO2(101) slab. It was found that the energy barrier of the rate-determining step, or the removal of adsorbed OH, was comparable to (or only slightly lower than) that of the pristine surfaces, indicating that defects play only a minor role in enhancing the ORR activity. In other words, it was suggested that oxygen vacancies and nitrogen dopants contributed to the emergence of ORR activity by enhancing the electrical conductivity of ZrO2 rather than by forming high quality active sites. Simple models are suitable for experimentally confirming the results of theoretical calculations and for understanding the active sites and the electron conduction paths separately. Therefore, we attempted to prepare nitrogen doped ZrOx nanofilms by RF magnetron sputtering method with different targets and atmospheres and to investigate their potential as model electrodes.ZrOx thin films of ca. 3-5 nm thickness were prepared by RF magnetron sputtering method using glassy carbon (GC) plates as substrates and ZrN or Zr metal plates as targets under Ar, Ar+O2 and Ar+N2. The sputtering power, the deposition time, and the substrate heating temperature were 100 W, 10 min, and 300 ℃, respectively. The flow rates of Ar, O2, and N2 gas were controlled to keep the total chamber pressure at approximately 0.6 Pa. When the gases were mixed, the partial pressure ratio was set to 1:1. Electrode prepared with a ZrN target in Ar was denoted as "ZrN_Ar", and electrodes prepared with a Zr target in Ar:O2 and Ar:N2 were denoted as "Zr_Ar+N2" and "Zr_Ar+O2", respectively. A conventional three-electrode cell was used for electrochemical measurements with Reversible Hydrogen Electrode (RHE) as a reference and a GC plate as a counter electrode in 0.5 M sulfuric acid at 30 ℃. The oxygen reduction current density i ORR (geometric area standard) was calculated by subtracting the current in N2 from the current in O2.Figure 1 shows the effect of sputtering condition on potential-ORR current curves of the ZrOx thin film electrodes. For comparison, the result of the GC substrate only is also plotted as "GC only." The ORR activity of the ZrN_Ar was lower than that of the GC only. In addition, the current of the steady-state cyclic voltammogram of the ZrN_Ar was smaller than that of the GC only. This may be due to the electrochemical oxidation of ZrN surface and the formation of an insulating layer without active sites, presumably Zr hydroxide. On the other hand, the onset potential of the Zr_Ar+N2 and the Zr_Ar+O2 for the ORR were higher than that of the GC only and the Zr_Ar+N2 showed highest ORR activity. The steady-state cyclic voltammograms of the Zr_Ar+N2 and the Zr_Ar+O2 were larger than that of GC only, revealing that these electrodes might have high conductivities. In addition, XPS measurements suggest that the Zr_Ar+N2 contains nitrogen and the Zr_Ar+N2 and the Zr_Ar+O2 have oxygen vacancies. These results suggested that their high ORR activities were caused by nitrogen doping and oxygen defects. Therefore, the electrodes prepared by RF magnetron sputtering method may be able to separate the active sites from the electron conduction by changing the sputtering conditions such as film thickness.AcknowledgementThe authors thank the financial support of the New Energy and Industrial Technology Development Organization (NEDO).References(1) A. Ishihara et al., J. Phys. Chem. C, 123, 18150 (2019).(2) M. Chisaka et al., ACS Omega, 2, 678 (2017).(3) S. Muhammady et al., J. Phys. Chem. C, 126, 15662 (2022). Figure 1

Growth mechanism and field emission of B doped AlN films

This paper highlights the effect of boron dopant on the field emission and growth mechanism of AlN films. The films have been grown by reactive RF magnetron sputtering method. For undoped films, columnar AlN structure was obtained. In the case of boron doped AlN films, the structure growth proceeded gradually through four layers of different thicknesses and structures. It was found that boron favors the formation of an amorphous layer within which oxygen and boron based precipitates develops, retarding the growth of columnar morphology. Depth profiling X-ray photoelectron spectroscopy analyses confirm the presence of B-O, B-N, Al-B and Al-O groups.The study on the field emission (FE) properties of undoped and B doped AlN films on Si substrates indicates that the addition of boron allow to improve FE properties with low turn on field of 2.6 V/μm and low threshold filed of 3.07 V/μm. Such good field emission properties can be attributed to the formation of densely nanograined surface and the appearance of boron based groups.

Effect of grain size on ferroelectric and dielectric properties of Bi3.25La0.75Ti3O12 thin films prepared by rf-magnetron sputtering

[Formula: see text][Formula: see text]Ti3[Formula: see text](BLT) thin films are promising materials used in non-volatile memories. In this work, BLT films were deposited on Pt(111)/Ti/SiO2/Si substrates by rf-magnetron sputtering method followed by annealing treatments. The microstructures of BLT thin films were investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). With the increase in annealing temperature, the grain size increased significantly and the preferred crystalline orientation changed. A well-saturated hysteresis loop with a superior remnant polarization of 15.4 [Formula: see text]C/cm2 was obtained for BLT thin films annealed at 700∘C. The results show that the dielectric constant decreased with the increase in grain sizes.

Growth, Characterization, and Application of Vertically Aligned Carbon Nanotubes Using the RF-Magnetron Sputtering Method.

The aim of this work is to synthesize and characterize a nanostructured material with improved parameters suitable as a chemiresistive gas sensor sensitive to propylene glycol vapor (PGV). Thus, we demonstrate a simple and cost-effective technology to grow vertically aligned carbon nanotubes (CNTs) and fabricate a PGV sensor based on Fe2O3:ZnO/CNT material using the radio frequency magnetron sputtering method. The presence of vertically aligned carbon nanotubes on the Si(100) substrate was confirmed by scanning electron microscopy and Fourier transform infrared (FTIR), Raman, and energy-dispersive X-ray spectroscopies. The uniform distribution of elements in both CNTs and Fe2O3:ZnO materials was revealed by e-mapped images. The hexagonal shape of the ZnO material in the Fe2O3:ZnO structure and the interplanar spacing in the crystals were clearly visible by transmission electron microscopy images. The gas-sensing behavior of the Fe2O3:ZnO/CNT sensor toward PGV was investigated in the temperature range of 25-300 °C with and without ultraviolet (UV) irradiation. The sensor showed clear and repeatable response/recovery characteristics in the PGV range of 1.5-140 ppm, sufficient linearity of response/concentration dependence, and high selectivity both at 200 and 250 °C without UV radiation. This is a basis for concluding that the synthesized Fe2O3:ZnO/CNT structure is the best candidate for use in PGV sensors, which will allow its further successful application in real-life sensor systems.

Study the hall effect and DC conductivity of CdSe and Te doped CdSe thin films prepared by RF magnetron sputtering method

CdSe and CdSe:Te thin films were grown on Si p-type substrates by RF magnetron sputtering method. The doping percentage of Tellurium (Te) in CdSe was 7% for the CdSe:Te thin film. The results show that after the doping of Te in the CdSe thin film, the conductivity changes from n-type to p-type and the mobility of the CdSe thin film increased. The conductivity of Te doped CdSe was found to be in order of 10−6 Ω−1 cm−1, while without doping it was 10−5 Ω−1 cm−1. X-ray diffraction (XRD) confirmed the presence of CdSe, Te and Si.

Advanced nano-texture, optical bandgap, and Urbach energy analysis of NiO/Si heterojunctions

Due to the large number of industrial applications of transparent conductive oxides (TCOs), this study focuses on one of the most important metal oxides. The RF-magnetron sputtering method was used to fabricate NiO thin films on both quartz and silicon substrates at room temperature under flow of Argon and Oxygen. The sputtered samples were annealed in N2 atmosphere at 400, 500, and 600 °C for 2 hours. Using the AFM micrographs and WSXM 4.0 software, the basic surface parameters, including root mean square roughness, average roughness, kurtosis, skewness, etc., were computed. Advanced surface parameters were obtained by the Shannon entropy through a developed algorithm, and the power spectral density and fractal succolarity were extracted by related methods. Optical properties were studied using a transmittance spectrum to achieve the optical bandgap, absorption coefficient, Urbach energy, and other optical parameters. Photoluminescence properties also showed interesting results in accordance with optical properties. Finally, electrical characterizations and I–V measurements of the NiO/Si heterojunction device demonstrated that it can be used as a good diode device.

Investigation the effect of dopant Te on CdSe thin films deposited by RF magnetron sputtering method

CdSe and CdSe:Te thin films were grown on glass substrates by RF magnetron sputtering. The doping percentage of Tellurium (Te) in CdSe was 7% for the CdSe:Te thin film. The microscopic images of the films were found to be uniform and homogeneous in nature with a uniform grain and no cracks, and the grain size of CdSe was higher than CdSe:Te thin film. CdSe:Te thin film shows a higher absorption coefficient compared to CdSe in the visible region. The Energy band gaps were found to be 2.01 and 1.73 eV for CdSe and CdSe:Te thin films, respectively. The incorporation of Te atom into the CdSe structure has enhanced the mobility and changed the type of conductivity from n-type to p-type.

Optimization of Pulsed Laser Ablation and Radio-Frequency Sputtering Tandem System for Synthesis of 2D/3D Al2O3-ZnO Nanostructures: A Hybrid Approach to Synthesis of Nanostructures for Gas Sensing Applications.

In this paper, a unique hybrid approach to design and synthesize 2D/3D Al2O3-ZnO nanostructures by simultaneous deposition is presented. Pulsed laser deposition (PLD) and RF magnetron sputtering (RFMS) methods are redeveloped into a single tandem system to create a mixed-species plasma to grow ZnO nanostructures for gas sensing applications. In this set-up, the parameters of PLD have been optimized and explored with RFMS parameters to design 2D/3D Al2O3-ZnO nanostructures, including nanoneedles/nanospikes, nanowalls, and nanorods, among others. The RF power of magnetron system with Al2O3 target is explored from 10 to 50 W, while the ZnO-loaded PLD's laser fluence and background gases are optimized to simultaneously grow ZnO and Al2O3-ZnO nanostructures. The nanostructures are either grown via 2-step template approach, or by direct growth on Si (111) and MgO<0001> substrates. In this approach, a thin ZnO template/film was initially grown on the substrate by PLD at ~300 °C under ~10 milliTorr (1.3 Pa) O2 background pressure, followed by growth of either ZnO or Al2O3-ZnO, using PLD and RFMS simultaneously under 0.1-0.5 Torr (13-67 Pa), and Ar or Ar/O2 background in the substrate temperate range of 550-700 °C. Growth mechanisms are then proposed to explain the formation of Al2O3-ZnO nanostructures. The optimized parameters from PLD-RFMS are then used to grow nanostructures on Au-patterned Al2O3-based gas sensor to test its response to CO gas from 200 to 400 °C, and a good response is observed at ~350 °C. The grown ZnO and Al2O3-ZnO nanostructures are quite exceptional and remarkable and have potential applications in optoelectronics, such in bio/gas sensors.

Investigation on photovoltaic performance of Cu2SnS3 thin film solar cells fabricated by RF-sputtered In2S3 buffer layer

A two-step process was used to prepare Cu2SnS3 films in this study: first, precursor stacks were deposited using a magnetron sputtering technique, and then the stacks were annealed in sulfur-containing atmosphere at various times. Utilizing a variety of characterization techniques, it was thoroughly examined how sulfurization time affected the films’ structural, morphological, optical, and electrical characteristics. X-ray diffraction and Raman spectroscopy measurements indicated that two structural polymorphs (tetragonal and monoclinic) of Cu2SnS3 co-existed in the films. Surface and cross-sectional images obtained by scanning electron microscopy showed that the microstructures of the films were entirely changed to well-grown crystal structures at 30 min and 40 min sulfurization times. In2S3/Cu2SnS3 stacks were prepared by the deposition of In2S3 films on the absorber layers sulfurized for 30 and 40 min by RF magnetron sputtering method. The fabrication of Ni/Al/Ni/AZO/i:ZnO/In2S3/Cu2SnS3/Mo/SLG-structured devices was done using both thermally annealed and non-annealed In2S3/Cu2SnS3 stacks. Secondary ion mass spectroscopy studies of the devices revealed that the indium diffused from In2S3 layer into the Cu2SnS3 absorber to a certain depth. The efficiency values of the devices were found to have been slightly enhanced with the annealing of the In2S3/Cu2SnS3 stacks. The solar cell with the maximum efficiency (η) of 3.12 %, open-circuit voltage (VOC) of 0.265 mV, short-circuit current (JSC) of 37.90 mA/cm2, and fill factor (FF) of 0.31 was produced by thermally annealed In2S3/Cu2SnS3 stack with an absorber layer sulfurized for 40 min.

Bipolar Switching Properties of the Transparent Indium Tin Oxide Thin Film Resistance Random Access Memories.

In this study, the bipolar switching properties and electrical conduction behaviors of the ITO thin films RRAM devices were investigated. For the transparent RRAM devices structure, indium tin oxide thin films were deposited by using the RF magnetron sputtering method on the ITO/glass substrate. For the ITO/ITOX/ITO/glass (MIM) structure, an indium tin oxide thin film top electrode was prepared to form the transparent RRAM devices. From the experimental results, the 102 On/Off memory ratio and bipolar switching cycling properties for set/reset stable states were found and discussed. All transparent RRAM devices exhibited the obvious memory window and low set voltage for the switching times of 120 cycles. The electrical transport mechanisms were dominated by the ohmic contact and space charge limit conduction (SCLC) models for set and reset states. Finally, the transmittances properties of the transparent ITO/ITOX/ITO RRAM devices for the different oxygen growth procedures were about 90% according to the UV-Vis spectrophotometer for the visible wavelength range.

Effect of tantalum addition on the mechanical properties of tungsten/tantalum composite thin films

Tungsten (W) when used as a plasma-facing material (PFM) in a tokamak will face harsh neutron radiation and high-temperature fluctuations. Due to its ductile-to-brittle transition temperature (DBTT), W behaves as a brittle material in lower temperatures and thus helps in propagating cracks easily resulting in dust formation and failure of material. In this study, an attempt has been made to improve the ductility, hardness, and toughness of W thin films by adding tantalum (Ta) to it, resulting in composite thin films. W/Ta composite thin films deposited on reduced-activation ferritic martensitic steel (RAFM) steel by RF magnetron sputtering method are compared with W thin films deposited on the same substrate. Taguchi orthogonal array is used to get the best properties for the composite thin films and nanoindentation technique is used to evaluate the mechanical properties of developed thin films. With the least hardness of 7.19 Gpa, composite film hardness is 452% lesser than the maximum hardness of (39.54 Gpa) W films. The reduction in hardness for composite thin films has not depleted the toughness as the Ef/Es ratio is higher than cracking threshold of 1.3. The maximum plastic energy absorbed for yield by composite films during nanoindentation is (1710 mN nm) 14% higher than W thin film (1500 mN nm), indicating the composite film is a ductile and tougher than the W film.

P-type β-Ga2O3 films were prepared by Zn-doping using RF magnetron sputtering

The XRD patterns show that the peak position of the Zn-doped β-Ga 2 O 3 films shifts to lower angles with the substrate temperature decreasing from 700℃ to room temperature, indicating the incorporation of Zn into Ga 2 O 3 films. Because the ion radius of Ga 3+ is 0.61Å and Zn 2+ is 0.74Å, the lattice spacing expanses with the increase of Zn concentration and thus the diffraction angle of the characteristic peak becomes smaller. The photoelectric response measurements show that the Zn-doped β-Ga 2 O 3 film based photodetectors manifest much lower dark-current and higher photo-to-dark current ratio. • P-type Ga 2 O 3 films were obtained by Zn doping using radio frequency magnetron sputtering method. • The doping concentration of Zn has a close relationship with temperature. • Zn-doped β-Ga 2 O 3 based photodetector manifested much lower dark-current and higher photo-to-dark current ratio. Zn-doped Ga 2 O 3 films were prepared using RF magnetron sputtering method at various deposition temperatures. Hall measurement demonstrated the present Zn-doped β-Ga 2 O 3 film was p -type conductivity. The XRD and XRF measurements showed the Zn dopant concentration increased with the decrease of temperature so that the position of the characteristic peak shifted to lower angles. The UV absorption spectra showed that the bandgaps became narrower with the doping concentration of Zn atom increasing. The pure and Zn-doped β-Ga 2 O 3 films were used to fabricate the photodetectors with MSM structure, respectively. The photoelectric response measurements showed that the Zn-doped specimen manifested much lower dark-current and higher photo-to-dark current ratio, but slower photoresponse speed.

Low-temperature electrical transport properties of La doped BaSnO&lt;sub&gt;3&lt;/sub&gt; films

A series of Ba&lt;sub&gt;0.94&lt;/sub&gt;La&lt;sub&gt;0.06&lt;/sub&gt;SnO&lt;sub&gt;3&lt;/sub&gt; thin films are deposited on MgO(001) single crystal substrates by RF magnetron sputtering method, and their structure and electrical transport properties are systematically investigated. All films reveal degenerate semiconductor (metal) characteristics in electrical transport properties. In the high-temperature region (&lt;inline-formula&gt;&lt;tex-math id="M8"&gt;\begin{document}$T &gt; {T_{\min }}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M8.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M8.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, where &lt;inline-formula&gt;&lt;tex-math id="M9"&gt;\begin{document}${T_{\min }}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M9.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M9.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; is the temperature at which the resistivity reaches a minimum value), the resistivity of each film increases with temperature, and exhibits a linear relationship with the square of the temperature. In the low-temperature region (&lt;inline-formula&gt;&lt;tex-math id="M10"&gt;\begin{document}$T &lt; {T_{\min }}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M10.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M10.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;), the resistivity increases with decreasing temperature and varies linearly with &lt;inline-formula&gt;&lt;tex-math id="M11"&gt;\begin{document}$ \ln T $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M11.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M11.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;. This temperature dependent behavior of resistivity cannot be explained by the general electron-electron interaction or weak localization effects in homogeneous disordered conductors and nor by Kondo effect. After quantitative analysis, it is found that the &lt;inline-formula&gt;&lt;tex-math id="M12"&gt;\begin{document}$ \ln T $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M12.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M12.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; behavior of resistivity at low temperatures can be explained by the electron-electron Coulomb interaction effect in the presence of granularity. In addition, it is found that the Hall coefficient &lt;inline-formula&gt;&lt;tex-math id="M13"&gt;\begin{document}$ {R_{\text{H}}} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M13.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M13.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; also varies linearly with &lt;inline-formula&gt;&lt;tex-math id="M14"&gt;\begin{document}$ \ln T $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M14.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="22-20231082_M14.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; for the Ba&lt;sub&gt;0.94&lt;/sub&gt;La&lt;sub&gt;0.06&lt;/sub&gt;SnO&lt;sub&gt;3&lt;/sub&gt; film, which also quantitatively accords with the theoretical prediction of the electron-electron Coulomb interaction effects in the granular metals. The results of cross-section high-resolution transmission electron microscope indicate that although the films have epitaxial structures as a whole, there are many strip-shaped amorphous regions in films, which makes the films have electrical transport properties similar to those of metal granular films. Our results provide strong support for the validity of the theory concerning the effects of Coulomb interaction on the conductivity and Hall coefficient in granular metals.

Band gap and interface engineering of ZnO@MoSe2heterojunction film and its light-matter coupling

The wide/narrow band gap semiconductor heterojunction promotes the coupling of light with matter and the rapid electron transport, which opens up a new research way for the construction of heterojunctions, photodetectors and quantum phenomena due to their excellent optical properties. Hereon, petal-like ZnO@MoSe2 and worm-like MoSe2 films were prepared by two-step/single-step RF magnetron sputtering method. Combined with the experimental results and the finite difference time domain (FDTD) simulation, it is proven that the 1T and 2H mixed phase MoSe2 can provide low energy growth sites for ZnO. ZnO@MoSe2 longitudinal n-p heterojunctions can form super-fast carrier transfer channels, enhancing the luminescence properties of heterojunctions in near-Gaussian fields. Moreover, both MoSe2 and ZnO@MoSe2 films show saturation absorption phenomenon with the coefficients of 0.43 × 10−7 mW−1 and 0.18 × 10−7 mW−1, respectively. The saturation absorption coefficient of ZnO@MoSe2 films is reduced due to Pauli blocking, which is caused by the electron transfer from the conduction band of MoSe2 to the conduction band of ZnO. The synthesized ZnO@MoSe2 films can be used in all optical switching, passive mode locking and other fields.

Effect of Oxygen Percentage on the Energy Band Gap of Ga2O3 Thin Films Deposited by RF Magnetron Sputtering Method

Effect of Oxygen Percentage on the Energy Band Gap of Ga2O3 Thin Films Deposited by RF Magnetron Sputtering Method

Growth of the ternary Pb(Mn,Nb)O3–Pb(Zr,Ti)O3 thin film with high piezoelectric coefficient on Si by RF sputtering

AbstractIn this study, ternary ferroelectric 0.06Pb(Mn1/3Nb2/3)O3–0.94Pb(Zr0.48Ti0.52)O3 (PMN–PZT) thin film with high piezoelectric coefficient were grown on La0.6Sr0.4CoO3‐buffered Pt/Ti/SiO2/Si substrate by RF magnetron sputtering method. The phase and domain structure along with the macroscopic electrical properties were obtained. Under the optimized temperature of 550°C and sputtering pressure 0.9 Pa, the PMN–PZT film owned large remnant ferroelectric polarization of 62 μC/cm2. In addition, the PMN–PZT film had polydomain structures with fingerprint‐type nanosized domain patterns and typical local piezoelectric response. Through piezoelectric force microscopy, the PMN–PZT thin film at nanoscale exhibited obvious domain reversal when subjected to in situ poling field. It was further found that the quasi‐static piezoelectric coefficient of the PMN–PZT thin film reached 267 pC/N, which was about twice to that of the commercial PbZrO3–PbTiO3 (PZT) thin film. The optimized relaxor ferroelectric thin film PMN–PZT on silicon with global electrical properties shows great potential in the piezoelectric micro‐electro‐mechanical systems applications.

Influence of deposition power and annealing on the performance of RF-sputtered SnS for infrared photodetection

Tin sulfide has shown their great potential in electronic and photonic systems due to its unique optoelectronic properties, less toxic nature, cost-effective and economically earth-abundant elements. The multivalence of Sn and stereochemical activity endow it with rich phase spaces and susceptible internal structures, which in turn directly affect its properties. In this paper, optimization studies towards the influence of RF power and post-deposition annealing temperature on the micro structure and photodetection performance of SnS are achieved by RF magnetron sputtering method. The structural characterizations confirm the significance of RF power for phase formation and photoelectric conversion ability. The optical band gap shifts from 1.41 eV to 1.30 eV as RF power increasing from 30 W to 50 W, in the meantime, the optoelectronic performances such as responsivity and specific detectivity are subsequently improved to be 226.55 mA/W and 1.76 × 1010 Jones. Further, the variations in infrared photodetection performance correlated with the annealing temperature exhibite a more well-behaved photoresponse at 300 °C. The results pave the way to discern the growth − structure − property relationships and then guide potencial applications of tin sulfide family.

(Digital Presentation) Oxygen Evolution Reaction on Non-Precious Metal Oxide-Based Electrocatalysts With and Without Low Potential Scan in Acidic Solution

Hydrogen energy ministerial meeting (H2 EM 2021) was held on Oct. 4, 2021 by the ministry of economy, trade and industry (METI) of Japanese government as online special event with cabinet members and officials from 29 countries, regions, and organizations. In the industrial session, 4 sessions were held, and the water electrolysis was one of the themes of industrial session. Panelists from several countries introduced state-of-art technologies of water electrolyzer [1]. In our previous study, the hydrogen producing from renewable energies is called as “Green Hydrogen” [2].Proton exchange membrane water electrolysis (PEMWE) has partly commercialized and recently applied its system for the Power-to-Gas (PtG). However, conventional anode is precious metal oxide such as IrO2 and the cost of raw material is expensive. From this point of view, the non-precious metal oxide anode should be required for green hydrogen production. We focused on tantalum and molybdenum oxide-based electrocatalyst (TaOx and MoOx) and have studied its catalytic activity for oxygen evolution reaction (OER) [3]. Moreover, TaOx with Mn addition showed much higher the OER activity than TaOx [4]. In this study, we have applied for MoOx with Mn addition for investigating the catalytic activity for the OER in acidic solution.Ti rod was used as substarate. MoOx was prepared by RF magnetron sputtering method. In the case of fabrication for Mn-MoOx, Mo metal piece for 40% surface area was set on the Mn disc as additional material. Each partial pressure of Ar and O2 gas was adjusted to 0.15 Pa in fabrication of Mn-MoOx. The substrate heating temperature was constant at 673 K during sputtering. We used conventional three electrode cell with each sample as working electrode while the reversible hydrogen electrode (RHE) and carbon plate were used as reference and counter electrode to demonstrate the electrochemical measurement in 1 M H2SO4 solution with saturated nitrogen atmosphere at 303 K. Several samples were demonstrated pretreatment from 0.05 to 1.2 V vs. RHE before the measurement of OER. The slow scan voltammetry was performed from 1.2 to 2.0 V to evaluate the OER activity. We also carried out electrochemical impedance spectroscopy (EIS) to obtain resistance components and semiconducting properties. In addition, samples before and after electrochemical measurement were analyzed by SEM-EDX and XPS.Figure 1 shows the Tafel plots of OER on Mo oxide-based electrocatalysts with and without Mn addition. The current density was based on geometric surface area. In the case of sample performing pretreatment, the Mn-MoOx with pretreatment (Mn-MoOx(Pre)) has obviously higher OER current than MoOx with pretreatment (MoOx(Pre)). Moreover, Mn-MoOx has higher OER current than Mn-MoOx(Pre), and the Tafel slope of OER on Mn-TaOx was 79 mV dec-1 the while the that on the Mn-MoOx(Pre) was 147 mV dec-1. From the results of EIS, the charge transfer resistance of Mn-MoOx was much smaller than that of Mn-MoOx(Pre) while the film resistance of was similar to that of Mn-MoOx(Pre). The results from SEM-EDX revealed that Mn amount in Mn-MoOx after the electrochemical measurement was constant compared to that before electrochemical measurement while Mn amount in Mn-MoOx(Pre) after electrochemical measurement was decreased compared to that before electrochemical measurement. From results from XPS analysis, Mn ratio in the Mn-MoOx after electrochemical measurement was constant compared to that before electrochemical measurement while Mn amount in Mn-MoOx(Pre) after electrochemical measurement was decreased compared to that before electrochemical measurement. Therefore, Mn species still remained on both surface and bulk in the case of Mn-MoOx while it was decreased in the case of Mn-MoOx(Pre). In Fig. 1, The peak over 1.5 V was detected from Tafel plots of both Mn-MoOx and Mn-MoOx(Pre). This peak corresponded to redox peak of Mn(III)/Mn(IV) [5], and it implied that Mn species affected on the OER activity. However, the electric charge of Mn(III)/Mn(IV) of Mn-MoOx was smaller than that of Mn-MnOx(Pre), and it is suggested that not only Mn oxide but also other species such as Mn-Mo compound oxide reacts as an active site of OER on Mn-MoOx.Acknowledgement: This work is partially supported by the Suzuki Foundation.Reference https://www.meti.go.jp/english/press/2021/1008_001.html Ota, A. Ishihara, K. Matsuzawa, and S. Mitsushima, Electrochemistry, 78, 970 (2010). Matsuzawa, S. Hirayama, K. Sumi, A. Ishihara, Abst. PRiME2020, I01F-2492, Online (2020). Matsuzawa, S. Hirayama, Y. Kohara, and A. Ishihara, ECS Trans, 104(8), 431 (2021).M. Morita, C. Iwakura, and H. Tamura, Electrochim. Acta, 24, 357 (1979). Figure 1