• Korean Journal of Materials Research
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• v.19 no.11
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• pp.601-606
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• 2009

$BiFeO_3$ (BFO) thin films were prepared on $Pt/TiO_2/Si$ substrate by r.f. magnetron sputtering. The effects of deposition pressure on electrical properties were investigated using measurement of dielectric properties, leakage current and polarization. When BFO targets were prepared, Fe atoms were substituted with Mn 0.05% to increase electrical resistivity of films. (Fe+Mn)/Bi ratio of BFO thin films increases with increasing partial pressure of $O_2$ gas. The deposited films showed the only BFO phase at 10 mTorr, the coexistence of BFO and $Bi_2O_3$ phase at 30-50 mTorr, and the only $Bi_2O_3$ phase at 70 mTorr. The crystallinity of BFO films was reduced due to the higher Bi contents and the decrease of surface mobility of atoms at high temperature. The porosity and surface roughness of films increased with the increase of the deposition pressure. The films deposited at high pressure showed low dielectric constant and high leakage current. The dielectric constant of films deposited at various deposition pressures was 84${\sim}$153 at 1 kHz. The leakage current density of the films deposited at 10${\sim}$70 mTorr was about $7{\times}10.6{\sim}1.5{\times}10.2A/cm^2$ at 100 kV/cm. The leakage current was found to be closely related to the morphology and composition of the BFO films. BFO films showed poor P-E hysteresis loops due to high leakage current.

• Journal of Sensor Science and Technology
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• v.4 no.2
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• pp.51-57
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• 1995

Indium Tin Oxide (ITO) thin films have been fabricated by the rf magnetron sputtering technique with a target of a mixture $In_{2}O_{3}$ (90mol%) and $SnO_{2}$ (10mol%). We prepared ITO thin films with substrate temperature 100, 200, 300, 400, $500^{\circ}C$ and post-annealing temperature 300, 400, $500^{\circ}C$. And we analyzed X -ray diffraction patterns, electrical properties, transmission spectra and SEM photographs. As a result, the crystallinity, electrical conductivity and transmittance of ITO thin films were improved with increasing substrate temperature. But, as increasing post-annealing temperature in air, conductivity of the film was decreased. When the ITO thin film was fabricated with substrate temperature of $500^{\circ}C$ and thickness of $3000{\AA}$, its resistivity and transmittance were about $2{\times}10^{-4}{\Omega}cm$ and 85% or more, respectively.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.980-986
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• 2001

Bragg reflector type FBAR was fabricated on the Si(100) substrate. We measured a frequency response of the resonator at 5.2 GHz and analyzed it by numerical calculation considering actual acoustic losses of each layer in the structure. We fabricated nine layer Bragg reflector of W-SiO$_2$pairs using r.f. sputtering method and fabricated AlN piezoelectric and Al electrodes using pulsed dc sputtering. The return loss(S$_{11}$) of the fabricated Bragg reflector type FBAR was 12 dB at 5.38 GHz and the series resonance frequency(f$_{s}$) was 5.376 GHz and the parallel resonance frequency(f$_{p}$) was 5.3865 GHz. Effective electro-mechanical coupling constant (K$_{eff{^2}}$) and Quality factors(Q$_{s}$), the Figures of Merit of the resonator, were about 0.48% and 411, respectively. We extracted acoustic parameters of AlN piezoelectric and reflection coefficient of the Bragg reflector by numerical calculation. We could know that material acoustic impedance and wave velocity of AlN piezoelectric decreased for intrinsic value and the electromechanical coupling constant(K$_2$) value was very low owing to the poor quality of the AlN piezoelectric. Reflection coefficient of Bragg reflector was 0.99966 and reflection band was very wide from 2.5 to 9.5 GHz.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.44-50
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• 1986

Si-ZnO n-n heterojunction diodes were prespared by r.f diode sputtering of the sintered ZnO target on n-type Si single crystal wafers and their structures and electrical properties were studied. The films were grown orientedly with the c-axis of crystallites perpendicular to the substrate surface at low r.f. powder and grown to polycrystalline films with random orientation at high r. f. powder. The crystallite size increased with the increasing substrate temperture The oriented texture films only were used to prepare the photovoltaic diodes and these didoes showed the photovoltaic effect veing positive of the ZnO side for the photons in the wavelength range of 380-1450nm. The sign reversal of phootovoltage which is the property os isotype heterojunction was not observed because of the degeneration of the ZnO films. The diode showed the forward rectification when it was biased with the ZnO side positive. The current-voltage characteristics exhibited the thermal-current type relationship J∝exp(qV/nkT) with n=1.23 at the low forward bias voltage and the tunnelling-current type relationship J∝exp($\alpha$V) where $\alpha$ was constant independent of temperature at the high forward bias voltage. The crystallite size of ZnO films were influenced largely on the photovoltaic properties of diodes ; The diodes with the films of the larger crystallites showed the poor photovoltaic properties. This reason may be cosidered that the ZnO films with the large crystallites could not grow to the electrically continuous films because the thickness of films was so thin in this experiment.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1589-1592
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• 1994

We developed the ion plating system, consisted of the Facing Target Magnetron Sputtering System and the r.f, electrode of the coil type, which was available to control the reactive and the adhesion between thin film and substrate, and studied about the discharge characteristics and the optimum condition in order to form the high quality thin film. The characteristics of discharge and plasma was measured as Double Probe and Electrostatic Retarding Grid Analyzer. The incident ion energy on the substrate was increased as the increasing r.f power, bias voltage. By the r.f electrode, the ionization rate of the sputtered particles was about 75%, and the mean incident ion energy depend on the value which was difference between the plasma potential and biased substrate potential.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.70-73
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• 2002

Thin films of vanadium oxide($VO_{x}$) have been deposited by r.f. magnetron sputtering from $V_{2}O_{5}$ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio of 0% and 8% is adopted. Crystal structure, chemical composition, molecular structure and optical properties of films sputter-deposited under different oxygen gas pressures and in-situ annealed in vacuum at $400^{\circ}C$ for 1h and 4h are characterized through XRD. RBS, FTlR and optical absorption measurements. The films as-deposited are amorphous and those annealed for time longer than 4h are polycrystalline. $V_{2}O_{5}$ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric $V_{2}O_{5}$. When annealed at $400^{\circ}C$, the as-deposited films are reduced to a lower oxide. It is observed that the oxygen atoms located on the V-O plane of $V_{2}O_{5}$ layer participate more readily in the oxidation and reduction process. The optical transmission of the films annealed in vacuum decreases considerably than the as-deposited films and the optical absorption of all the films increases rapidly between 400 and 550nm.

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.198-205
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• 2003

$Ba_{0.66}Sr_{0.34}TiO_3$ thin films and seed-layers were deposited on $Pt/Ti/SiO_2/Si$substrate by R.F. magnetron sputtering method. Effects of various substrate temperature conditions on electrical properties (such as capacitance and leakage current) of BST thin films were studied. The effect of seed-layer was also studied. When seed-layer was inserted between BST and Pt, the crystallization of the BST thin films was considerably improved and the processing temperature was lowered. Compared to the pure BST thin films, dielectric constant, dielectric loss, and leakage current of BST thin films deposited on the seed-layer were considerably improved. It could be revealed that electrical properties are influenced by the substrate temperatures of BST thin films and are enhanced by the seed-layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.729-732
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• 2001

In this study, the effect of oxygen partial pressure on the electrical properties of vanadium oxide(VO$_{x}$) thin films were investigated. The thin films were prepared by r.f. magnetron sputtering from V$_2$O$_{5}$ target in a gas mixture of argon and oxygen. The oxygen partial pressure ratio is changed from 0% to 8%. I-V characteristics were distinguished between linear and nonlinear region. In the low field region the conduction is due to Schottky emission, while at high fields it changes to Fowler-Nordheim tunneling type conduction. The conductivity measurements have shown an Arrhenius dependence of the conductivity on the temperature.ure.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.222-226
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• 1998

$Cu_3N$ film deposited on silicon oxide substrate by r.f. reactive sputtering technique. Synthesis and properties of copper nitride film were investigated for its possible application to Cu metallization as adhesive interlayer between copper and $SiO_2. Cu_3N$ film was synthesized at the substrate temperature ranging from $100^{\circ}C$ to $200^{\circ}C$ and at nitrogen gas ratio above $X_{N2}=0.4. Cu_3N, CuN_x$, and FGM-structured $Cu/CuN_x$ films prepared in this work passed Scotch-tape test and showed improved adhesion property to silicon oxide substrate compared with Cu film. Electrical resistivity of copper nitride film had a dependency on its lattice constant and was ranged from 10-7 to 10-1 $\Omega$cm. Copper nitride film was, however, unstable when it was annealed at the temperature above $400^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.81-83
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• 1992

The superconducting thin films deposited on $SiO_x$ substrate by R.F magnetron sputter using $YBa_2Cu_3O_x$ single target have been made and annealed at $940^{\circ}C$ for 30 min. The thickness of films were 1000-2000${\AA}$ with a rate of 20-25${\AA}/min$ and superconducting properties of thin films depended on the compositions of pre-annealed the thin films. It has been analyzed by SEM photo-analysis and X-ray diffraction patterns of these samples obtained under the various conditions of this sputtering methods. and recognized the supperconducting thin films by electric properties.