[en] MgO thin films were deposited on SiO₂(100) substrates by using electrostatic spray pyrolysis and Mg(tmhd)₂ as the precursor. The growth rates of the films varyed from 34 to 87 A/min and were measured for various substrate and guide temperatures. X-ray diffraction analysis provide evidence that the MgO films deposited at temperatures as low as 400 ∼ 500 .deg. C had preferred orientation to (100) plane perpendicular to the substrate surface. X-ray photoelectron spectroscopy and Auger electron spectroscopy data indicated that there were few organics incorporated in the films

[en] MgO thin films were deposited with r.f. magnetron sputtering method. Deposition parameters such as working pressure and r.f. power were found to influence properties of deposited films. As working pressure increased, crystallinity deteriorated while rms surface roughness decreased and film density increased. In this case, grain size did not change much compared with the case of r.f. power. On the other hand, as r.f. power increased, both grain size and rms surface roughness increased while film density decreased. An increase of r.f. power improved crystallinity a little and induced (1 0 0) preferred orientation. But the amount of variation was small compared with the case of pressure. Sputtered MgO thin films were hydrated by exposing in the humid ambience with 80% relative humidity at room temperature. Hydration reaction produced clusters, Mg(OH)₂, on the surface of the films. Hydration also occurred in the inner part of MgO thin film. The entire hydrated region was observed to be approximately 2 nm thick. Therefore, the factors that influence hydration seem to be density and grain size of MgO films. MgO film with high density can restrict inter-diffusion of Mg atom and H₂O, which is an important process for hydration. A reduction of grain size increased the area of grain boundary, which provided nucleation sites of hydration reaction as well as the short path of inter-diffusion of Mg atoms and H₂O molecules. From the results, the relation between deposition condition and hydration characteristics of MgO thin films can be established

[en] To fabricate lateral-field excitation (LFE)-mode solid mounted resonator (SMR)-type film bulk acoustic resonators (FBARs), piezoelectric ZnO layers were deposited in an RF magnetron sputtering system. Control of the crystallinity, microstructure and electric properties of the piezoelectric layers was essential for fabricating high-quality LFE-mode SMR-type FBARs. In the appropriate deposition condition for FBAR devices, ZnO thin films with highly c-axis-preferred orientation (XRD rocking curve, σ=2.17 deg. ), high resistivity of 10⁶ Ω cm and surface roughness of 10.6 A were deposited. Optimal substrate rotation was especially important for improvement of the c-axis-preferred orientation of ZnO films. Plasma properties such as the electron temperature, plasma density and saturated ion current were also analyzed for optimal ZnO deposition conditions using a Langmuir double-probe system. The resonator, for which the active piezoelectric area was 200x200 μm², consisted of 1.25-μm-thick ZnO film and a 110-nm Au electrode. Its series and parallel resonance frequencies appeared at 1.68 and 1.71 GHz, respectively, and the quality factor was 201.4±7.4

[en] Electroforming behaviours of Ta₂O₅ resistance switching memory cell with a diameter of 28 nm and different thickness (0.5-2.0 nm) of Ta₂O₅ layer have been examined. The devices showed a constant forming electric field of 0.54 V/nm regardless of Ta₂O₅ thickness. The electroforming with negative bias to top TiN electrode was ascribed to electric field- driven migration of oxygen vacancies, originally residing near the bottom interface, toward the top electrode interface and formation of conducting filaments. The estimated electroforming energy (0.094-0.14 eV) was favourably compared with the hopping energy of electrons from the V_O site to a nearby Ta site. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] This study examined the various physical, structural and electrical properties of SiO₂ doped Ge₂Sb₂Te₅ (SGST) films for phase change random access memory applications. Interestingly, SGST had a layered structure (LS) resulting from the inhomogeneous distribution of SiO₂ after annealing. The physical parameters able to affect the reset current of phase change memory (I_res) were predicted from the Joule heating and heat conservation equations. When SiO₂ was doped into GST, thermal conductivity largely decreased by ∼ 55%. The influence of SiO₂-doping on I_res was examined using the test phase change memory cell. I_res was reduced by ∼ 45%. An electro-thermal simulation showed that the reduced thermal conductivity contributes to the improvement of cell efficiency as well as the reduction of I_res, while the increased dynamic resistance contributes only to the latter. The formation and presence of the LS thermal conductivity in the set state test cell after repeated switching was confirmed.