Modelling and Optimization for Deposition of SiOxNy Films by Radio-Frequency Reactive Sputtering

SiOxNy films are deposited by reactive sputtering from a Si target in Ar/O2/N2 atmospheres. In order to achieve the control of film composition and to keep a high deposition rate at the same time, a new sputtering model based on Berg＇s work is provided for the condition of double reactive gases. Analysis based on this model shows that the deposition process can easily enter the target-poisoning mode when the preset gas flow （N2 in this work） is too high, and the film composition will change from nitrogen-rich to SiO2-like with the increase of oxygen supply while keeping the N2 supply constant. The modelling results are confirmed in the deposition process of SiOxNy. Target self-bias voltages during sputtering are measured to characterize the different sputtering modes. FTIR-spectra and dielectric measurements are used to testify the model prediction of composition. Finally, an optimized sputtering condition is selected with the O2/N2 flow ratio varying from 0 to I and N2 supply fixed at I sccm. Average deposition rate of 17nm/min is obtained under this selected condition, which has suggested the model validity and potential for industry applications.     

Target voltage behaviour of a vanadium-oxide thin film during reactive magnetron sputtering

This paper simulates reactive magnetron-sputtering in constant current mode in a Vanadium-O 2 /Ar system equipped with a DC power supply by adopting both kinetics model and Berg’s model.The target voltage during the reactive sputtering has been investigated as a function of reactive gas flow.Both experiments and simulations demonstrate a hysteresis curve with respect to the oxygen supply.The time-dependent variation of the target mode is studied by measuring the target voltage for various reactive oxygen gas flows and pre-sputtering times.The presputtering time increases with the increased initial target voltage.Furthermore,a corresponding time-dependent model simulating target voltage changes is also proposed.Based on these simulations,we find some relationships between the discharge voltage behaviour and the properties of the formed oxide.In this way,a better understanding of the target voltage changes during reactive sputtering can be achieved.We conclude that the presented theoretical models for parameter-dependent case and time-dependent case are in qualitative agreement with the experimental results and can be used to comprehend the target voltage behaviour in the deposition of vanadium oxide thin films.     

Engineering of electronic and optical properties of ZnO thin films via Cu doping

ZnO thin films doped with different Cu concentrations are fabricated by reactive magnetron sputtering technique. XRD analysis indicates that the crystal quality of the ZnO:Cu film can be enhanced by a moderate level of Cu-doping in the sputtering process. The results of XPS spectra of zinc, oxygen, and copper elements show that Cu-doping has an evident and complicated effect on the chemical state of oxygen, but little effect on those of zinc and copper. Interestingly, further investigation of the optical properties of ZnO:Cu samples shows that the transmittance spectra exhibit both red shift and blue shift with the increase of Cu doping, in contrast to the simple monotonic behavior of the Burstein–Moss effect. Analysis reveals that this is due to the competition between oxygen vacancies and intrinsic and surface states of oxygen in the sample. Our result may suggest an effective way of tuning the bandgap of ZnO samples.     

Excellent soft magnetic properties realized in FeCoN thin films

FeCoN soft magnetic thin films are prepared by using the reactive direct-current magnetron sputtering technique.It is found that the addition of N2 can reduce the coercivity of the FeCoN film,and excellent soft magnetic properties can be obtained when the ratio of N2 flow to total gas flow is 10%.The influences of texture,grain size,and stress on the magnetic properties and the high-frequency behaviors of the films are also discussed.     

High Ferroelectricities and High Curie Temperature of BiInO3PbTiO3Thin Films Deposited by RF Magnetron Sputtering Method

Properties of ferroelectric xBiInO_3-(1-x)PbTiO_3(xBI-(1-x)PT) thin films deposited on(101) SrRuO_3/(200)Pt/(200) MgO substrates by rf magnetron sputtering method and effects of deposition conditions are investigated.The structures of the xBI-(1-x)PT films are characterized by x-ray diffraction and scanning electron microscopy.The results indicate that the thin films are grown with mainly(001) orientation. The chemical compositions of the films are analyzed by scanning electron probe and the results indicate that the loss phenomena of Pb and Bi elements depend on the pressure and temperature during the sputtering process.The sputtering parameters including target composition, substrate temperature, and gas pressure are adjusted to obtain optimum sputtering conditions. To decrease leakage currents,2 mol% La_2 O_3 is doped in the targets. The P-E hysteresis loops show that the optimized xBI-(1-x)PT(x = 0.24) film has high ferroelectricities with remnant polarization2 P_r = 80μC/cm~2 and coercive electric field 2 E_C = 300 kV/cm. The Curie temperature is about 640℃. The results show that the films have optimum performance and will have wide applications.     

Relationship between bias voltage and microstructure as well as properties of CrAlYN films

In this work, a series of Cr Al YN films doped with 1 at.% yttrium were deposited by unbalanced reactive magnetron sputtering under different bias voltages. The effects of bias voltage on microstructure and properties of the Cr Al YN films were subsequently investigated. It is found that all the as-deposited films have similar chemical composition and crystalline structure. However, the bias voltage has significant impact on the mechanical properties and oxidation resistance of the resulting films. Namely, the film deposited at 100 V has the highest hardness and best oxidation resistance, which are mainly attributed to its denser structure and higher Al content than others. In addition, the film obtained at 100 V exhibits superior oxidation resistance even at 1000℃ , and good friction and wear properties at 600 and 800℃ , and the latter two are mainly ascribed to the formation of compact transfer layer on the worn surfaces. However, this film experienced obvious wear loss at low testing temperatures(i.e., 200 and 400℃ ) due to the serious abrasive wear.     

The Influence of Au-Doping on Morphology and Visible-Light Reflectivity of TiN Thin Films Deposited by Direct-Current Reactive Magnetron Sputtering

Ti, TiN and Au-TiN （Au content： from 0.5%to 7.7%） thin films were deposited on stainless steel substrates by dc reactive magnetron sputtering with a metal Ti target. The crystal structure, surface morphology and visiblelight reflectivity of the films for different film compositions are studied in detail. Distinctly different surface morphologies appear for the Ti, TiN and Au-TiN thin films. It can be observed that the surface morphology of the TiN film is affected by the Au-doping, when the Au content increases from 0% to 7.7%, surface roughness enlarges from 62.4 to 82.8 nm. Moreover, visible-light reflectivity varies significantly with increasing A u contents in the TiN films. However, the rettectivity of the TiN thin film at 550-800 nm is higher than that of the Au-TiN thin film. The present work illustrates the dependence of metal elements on the surface morphology and on the reflectivity of Au-TiN thin films. It is speculated that the addition of Au can suppress the formation and growth of TiN grains so that it changes the surface morphology and the Au-TiN thin film has potential applications in spectral selective coating.     

Influence of Inert Gas Pressure on Growing Rate of Nanocrystalline Silicon Film Prepared by Pulsed Laser Deposition

Nanocrystalline silicon film (nc-Si) was prepared by pulsed laser deposition in different inert gas atmospheres such as He, Ne and Ar. The influence of inert gas pressure on growing rate of the film was investigated. The results show that with increasing gas pressure, growing rate first increases and reaches its maximum and then decreases; the gas pressure at the maximum of growing rate is proportional to the reciprocal of atomic mass of gas. The rate maximum is 0.315 A/pulse when He gas pressure is 8.3 Pa. The dynamic process is analysed theoretically by means of resputtering from the film surface and scattering of ablated particles. Ehrthermore, our results are compared with those in the case of Ag target.     

Effect of Incident Intensity on Films Growth in Pulsed Laser Deposition

Incident intensity, defined by the amount of particles deposited per pulse, is an important parameter in the film growth process of pulsed laser deposition （PLD）. Different from previous models, we investigate the irreversible and reversible growth processes by using a kinetic Monte Carlo method and find that island density and film morphology strongly depend on pulse intensity. At higher pulse intensities, lots of adatoms instantaneously diffuse on the substrate surface, and then nucleation easily occurs between the moving adatoms resulting in more smaller-size islands. In contrast, at the lower pulse intensities, nucleation event occurs preferentially between the single adatom and existing islands rather than forming new islands, and therefore the average island size becomes larger in this case. Additionally, our results show that substrate temperature plays an important role in film growth. In particular, it can determine the films shape and weaken the effect of pulse intensity on film growth at the lower temperatures by controlling the mobility rate of atoms. Our results can match the related theoretical and experimental results.     

Thick c-BN films deposited by radio frequency magnetron sputtering in argon/nitrogen gas mixture with additional hydrogen gas

The excellent physical and chemical properties of cubic boron nitride(c-BN) film make it a promising candidate for various industry applications. However, the c-BN film thickness restricts its practical applications in many cases. Thus, it is indispensable to develop an economic, simple and environment-friend way to synthesize high-quality thick, stable c-BN films. High-cubic-content BN films are prepared on silicon(100) substrates by radio frequency(RF) magnetron sputtering from an h-BN target at low substrate temperature. Adhesions of the c-BN films are greatly improved by adding hydrogen to the argon/nitrogen gas mixture, allowing the deposition of a film up to 5-μm thick. The compositions and the microstructure morphologies of the c-BN films grown at different substrate temperatures are systematically investigated with respect to the ratio of H_2 gas content to total working gas. In addition, a primary mechanism for the deposition of thick c-BN film is proposed.     

Effect of the duty ratio on the indium tin oxide (ITO) film deposited by in-line pulsed DC magnetron sputtering method for resistive touch panel

The indium tin oxide (ITO) film was deposited on PET (polyethylene terephthalate) film using in-line pulsed DC magnetron sputtering system with different duty ratios. The reverse time and the frequency of pulsed DC power were changed to obtain the different duty ratios. From the electrical and optical properties such as the sheet resistance, resistivity, thickness and transmittance, the pulsed DC sputtered ITO/PET films were also superior to the DC sputtered ITO/PET films. The reverse time had little effect on the properties of the ITO/PET film and the frequency of pulsed DC power had an immerse effect on the properties of the ITO/PET films. The optimal ITO/PET film was obtained when the frequency was 200 kHz, the reverse time was 1 μs, and the duty ratio was about 80%.     

Investigation on the shockwave induced by surface arc plasma in quiescent air

The shockwave induced by surface direct-current （DC） arc discharge is investigated both experimentally and numer- ically. In the experiment, the shockwave generated by rapid gas heating is clearly observed from Schlieren images. The peak velocity of the shockwave is measured to be over 410 m/s; during its upright movement, it gradually falls to about 340 m/s; no remarkable difference is seen after changing the discharge voltage and the pulse frequency. In the modeling of the arc plasma, the arc domain is not simulated as a boundary condition with fixed temperature or pressure, but a source term with a time-varying input power density, which could better reflect the influence of the heating process. It is found that with a reference power density of 2.8× 1012 W/m2, the calculated peak velocity is higher than the measured one, but they quickly （in 30 Its） become agreed with each other. The peak velocity also rises while increasing the power density, the maximum velocity acquired in the simulation is over 468 m/s, which is expected to be effective for high speed flow control.     

Nitriding molybdenum： Effects of duration and fill gas pressure when using lO0-Hz pulse DC discharge technique

Molybdenum is nitrided by a 100-Hz pulsed DC glow discharge technique for various time durations and fill gas pressures to study the effects on the surface properties of molybdenum. X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, and atomic force microscopy （AFM） are used for the structural and morphological analysis of the nitrided layers. Vickers＇ microhardness tester is utilized to investigate surface microhardness. Phase analysis shows the formation of more molybdenum nitride molecules for longer nitriding durations at fill gas pressures of 2 mbar and 3 mbar （1 bar = 105 Pa）. A considerable increase in surface microhardness （approximately by a factor of 2） is observed for longer duration （10 h） and 2-mbar pressure. Longer duration （10 h） and 2-mbar fill gas pressure favors the formation of homogeneous, smooth, hard layers by the incorporation of more nitrogen.     

Effect of substrate temperature on microstructure and optical properties of single-phased Ag20 film deposited by using radio-frequency reactive magnetron sputtering method

Using a radio-frequency reactive magnetron sputtering technique, a series of the single-phased Ag20 films are deposited in a mixture of oxygen and argon gas with a flow ratio of 2：3 by changing substrate temperature （Ts）. Effects of the Ts on the microstructure and optical properties of the films are investigated by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. The single-phased Ag20 films deposited at values of Ts below 200℃ are （111） preferentially oriented, which may be due to the smallest free energy of the （111） crystalline face. The film crystallization becomes poor as the value of Ts increases from 100℃ to 225℃. In particular, the Ag20 film deposited at Ts=225℃ loses the （111） preferential orientation. Correspondingly, the film surface morphology obviously evolves from a uniform and compact surface structure to a loose and gullied surface structure. With the increase of Ts value, the transmissivity and the reflectivity of the films in the transparent region are gradually reduced, while the absorptivity gradually increases, which may be attributed to an evolution of the crystalline structure and the surface morphology of the films.     

Thermal analysis for the high duty cycle PIMS accelerator

To develop the high power proton linear accelerator for the Accelerator Driven System（ADS） program,the preliminary design of the Pi mode accelerating structure（PIMS） has been carried out.It is estimated that PIMS would heat up to 80 for low duty cycle（0.1%） without water-cooling,which is not acceptable thus water-cooling is demanded.The structure stability for the high duty cycle or even for CW operation is crucially important for the ADS application.Therefore,thermal analysis with water-cooling for a high duty accelerator in our ADS research is performed to control the frequency shift caused by a temperature rise.     

Asymmetric reversible diode-like resistive switching behaviors in ferroelectric BaTiO3 thin films

In this work, the resistive switching behaviors of ferroelectrictric BaTiO3/La0.67Sr0.33MnO3 .heterostructures de- posited by pulsed laser deposition are investigated. The BaTiO3 films show both well-established P-E hysteresis loops, and asymmetric reversible diode-like resistive switching behaviors, involving no forming process. It is found that both the ON/OFF ratio and the stability of resistive switching are substantially dependent on operation voltage （Vmax）. At a Vmax of 15 V, a large ON/OFF resistance ratio above 1000 is obtained at a Vmax of 15 V, which is able to maintain stability up to 70-switching cycles. The above resistive switching behaviors can be understood by modulating interface Schottky barriers as demonstrated by I-V curve fitting.     

脉冲直流偏压增强的高质量立方氮化硼薄膜的合成

采用磁增强活性反应离子镀系统成功地合成了立方氮化硼薄膜.通过给基片施加脉冲直流偏压以代替传统的射频偏压,增强了立方氮化硼的成膜稳定性,研究了基片的直流脉冲偏压、等离子体放电电流、通入气体流量比(Ar/N₂)和基片温度沉积参数对立方氮化硼薄膜形成的影响规律.结果表明:随着基片负偏压和放电电流的增大,薄膜中立方氮化硼的纯度提高,当基片负偏压为155V,放电电流为15A时,可获得几乎单相的立方氮化硼薄膜.基片温度为500℃和Ar/N₂流量比为10时,最有利于立方氮化硼 关键词： 立方氮化硼 活性反应离子镀 脉冲偏压     

Charge ordering modulations in a Bi0.4Ca0.6MnO3 film with a thickness of 110 nm

The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi0.4Ca0.6MnO3 film with a thickness of 110 nm at 103 K. Six different types of superlattice structures are observed using the selected-area electron diffraction （SAED） technique, while three of them match well with the modulation stripes in high-resolution transmission electron microscopy （HRTEM） images. It is found that the modulation periodicity and direction are completely different in the region close to the Bi0.4Ca0.6MnO3/SrTiO3 interface from those in the region a little further from the Bi0.4Ca0.6MnO3/SrTiO3 interface, and the possible reasons for this are discussed. Based on the experimental results, structural models are proposed for these localized modulated structures.     

Proposal for muon and white neutron sources at CSNS

The China Spallation Neutron Source （CSNS） is a large scientific facility with the main purpose of serving multidisciplinary research on material characterization using neutron scattering techniques. The accelerator system is to provide a proton beam of 120 kW with a repetition rate of 25 Hz initially （CSNSⅠ）, progressively upgradeable to 240 kW （CSNS-Ⅱ） and 500 kW （CSNS-Ⅱ＇）. In addition to serving as a driving source for the spallation target, the proton beam can be exploited for serving additional functions both in fundamental and applied research. The expanded scientific application based on pulsed muons and fast neutrons is especially attractive in the overall consideration of CSNS upgrade options. A second target station that houses a muon-generating target and a fast-neutron-generating target in tandem, intercepting and removing a small part of the proton beam for the spallation target, is proposed. The muon and white neutron sources are operated principally in parasitic mode, leaving the main part of the beam directed to the spallation target. However, it is also possible to deliver the proton beam to the second target station in a dedicated mode for some special applications. Within the dual target configuration, the thin muon target placed upstream of the fast-neutron target will consume only about 5% of the beam traversed; the majority of the beam is used for fast-neutron production. A proton beam with a beam power of about 60 kW, an energy of 1.6 GeV and a repetition rate of 12.5 Hz will make the muon source and the white neutron source very attractive to multidisciplinary researchers.     

Design study of a L-band DC photocathode gun

In this paper, we the design study of a L-band DC photocathode gun injector for the ERL （Energy Recovery Linac） test facility. The main parameters of the injector are energy of 2.3 MeV, a bunch length of 2 ps, and a normalized emittance of 2.1 mm.mrad.