Masaaki Yoshitake

The use of the ion beam current as a process control in the reactive sputtering of zirconium oxide

Abstract A Zr target is sputtered in an oxygen atmosphere by a reactive-ion-beam-sputtering technique. It has been found that, even at a constant oxygen flow, the residual oxygen pressure during sputtering can be extensively controlled by the Ar ion beam current used for sputtering. The relationship between these factors is expressed quantitatively. The films composition, structure and optical properties are also transformed from a metallic to an insulating state by the Ar ion beam current. This indicates that the ion beam current used for sputtering can be used as a sputtering parameter for process control. In addition, it is demostrated that, by only controlling Ar ion beam current, the film composition is dynamically modulated towards the surface direction in a single sputtering process. This shows that the technique is applicable to optical film coating.

Modification of ZnO crystal orientation in dual ion beam sputtering deposition

Abstract The effect of ion irradiation on ZnO thin films crystal orientation during dual ion beam sputtering deposition is studied. Glass and Si substrates are irradiated during depostion by oxygen and argon ions. The irradiating oxygen ions are swept away from the substrate by a cross-electric field to examine the effect of high energy neutral atoms on crystal orientation. Argon and oxygen positive ions prepared in a saddle field ion gun can effectively form c -axis orientation in ZnO film deposition. But oxygen high energy neutral atoms tend to deform the c -axis orientation of the films. ZnO film prepared by this method is useful in the production of devices with good piezoelectric and pyroelectric properties.

Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering

Abstract We have investigated the properties of gold-carbon composite thin films prepared by a plasma sputtering deposition using argon and methane mixture gas. These composite films have an uneven surface in submicron scale or consist of nano-scale particles of gold polycrystalline. Such morphological properties can be controlled by the sputtering voltage and the partial pressure of methane gas. The working electrode of electrochemical gas sensor has needed a stable gas sensitivity and a good gas selectivity. Our composite film is one of the excellent candidates for a thin film working electrode of electrochemical gas sensor. It is described that the output current of sensor is related to the preparation conditions of the thin films and increase linearly as the concentration of PH3 gas ranging from 0.1 to 1.0 ppm is increasing.

Electrical Resistivity and High-Field Magnetoresistance of Zr–N Film Thermometers

Temperature and magnetic field dependence of the resistivity of Zr-N sputtered films have been measured. The characteristics of Zr-N film, that they can be divided into two groups by the ratio of the resistance at helium and room temperatures, have been precisely investigated. There are marked differences in both the temperature dependence of resistance and in the magnetoresistance between the two groups. The temperature dependence of magnetoresistance of the films has been discussed within the framework of Anderson localization. The origin of magnetoresistance was also discussed.

PT THIN FILMS PREPARED BY LOW ENERGY PLASMA SPUTTERING

Abstract Platinum thin film has been prepared by low energy plasma sputtering deposition. Surface smoothness, stress in the film, crystal grain size and crystal orientation have been investigated for target voltages between 10 and 500 V. The effect of substrate temperature has also been studied. A minimum roughness of 1.1 nm was obtained with voltage of 20 or 30 V at room temperature. Auger analysis suggests that the deposition mechanism at 30 V is similar to the layer-by-layer (two-dimensional) deposition, while that at 100 V is significantly different. The formation of a very smooth surface is thought to be related to the layer-by-layer deposition process. The (111) oriented thin film was obtained at the target voltage of 30 V at room temperature.

Deposition of ZrC thin films and plasma-polymerized hydrocarbon films in the reactive magnetron sputtering process

Abstract ZrC films are sputter deposited by r.f. magnetron sputtering using an acetylene reactive gas. The relationship between the film properties and sputtering conditions is investigated using reactive gas pressure and r.f. power as sputtering parameters. Two distinct kinds of deposition processes—sputtering from a target and polymerization from acetylene—occur during sputtering. The relative importance of these processes depends on the sputtering conditions. Furthermore, these processes strongly affect the film composition and properties. The mechanism of these processes during sputtering is clarified in order to obtain ZrC films with a high hardness. The application of r.f. power as a sputtering parameter to obtain suitable properties of ZrC films is also investigated.

Thin Film Thermometer with Small Magnetoresistance

A zirconium nitride(Zr-N) thin film for cryogenic thermometer was fabricated by using a reactive rf-sputtering equipment. The Zr-N was deposited on a sapphire or a glass substrate. The composition ratio ofthe film could be changed by changing the sputtering condition such as partial pressure of N2. The Zr-N film, which had excess nitrogen(N>Zr), showed negative TCR (Temperature Coefficient of Resistance) and was classified into three groups by its RR (R4.2K/R300K) and MR (magnetoresistance). The group I (RR<3) showed negative MR and indicated logarithmic temperature dependence of the conductance. The group II (RR<IO) showed positive MR and its conductance was proportional to \(\sqrt{T}\) He temperatures. For the intermediate group (RR~5), the conductivity altered as \(\sqrt{T}+\ln(T)\). The MR changed once from negative to positive and finally became negative again with increasing magnetic field. In a magnetic field of 6 T, the temperature error at 4.2 K was less than 10 mK. These behavior of MR and conductance can be explained by the localization theory.

ZnO crystal orientation change by bias voltage application to substrate or target in ion beam sputtering

Abstract The effects of charged sputtered particles on the crystal orientation during ion beam sputtering deposition of zinc oxide films are presented. The formation of the necessary c -axis orientation was tried by controlling the kinetic energies of the sputtered charged particles in two different methods. In one method, a bias voltage is applied to three substrate materials: Corning 7059 glass, Si(100), and ZnS thin film, while in the other method, it is applied to a ZnO target. It is found that the existence of positively charged sputtered particles and the absence of negatively charged particles on the substrate are effective in forming c -axis orientation.

Origin of oscillatory magnetoresistance in Zr-N films

Abstract Zr-N films in the variable-range-hopping regions show an oscillatory magnetoresistance (MR). MR consists of a linear negative MR (LNMR) below 1.5T, a positive one above 1.5T and again a negative MR in higher field. We investigated the origin of LNMR. The LNMR of Zr-N films can be quantitatively interpreted by a quantum coherence effect that is characteristically seen in VRH regime.

A New Superconducting Planer Magnet Development from a Magnetic Shielding Device Made of NbTi-Cu Films

We have studied the magnetizing characteristics of large scale sheets (300×1000 mm) of various tickness with superconducting NbTi-Cu multilayer films up to 100 layers in vertical magnetic field: The number of NbTi layer (n) dependence on the maximum value of trapped flux density (BTM) were investigated. In region of 0.1 µm < the thickness of a NbTi layer (d) < 1 µm at the total thickness of NbTi layers (nd)=10 µm, BTM increased in proportion to the logarithm of n value. In case of d=0.1 µm and n=100, the value of BTM was 3 times larger than that of the multilayer film with d=1.0 µm and n=10.