Papers by Author: Chul Ho Park

Abstract: Pt/PZT/PbO/Si with the MFIS structure was deposited on the p-type (100) Si substrate by the r.f. magnetron sputtering method with Pb1.1Zr0.53Ti0.47O3 and PbO targets. From the X-ray photoelectron spectroscopy (XPS) results, we could confirm that the partial pressure ratio during PbO deposition affects the interface condition of PbO/Si and the chemical state of Pb existing at the surface of the PZT thin film. The maximum value of the memory window is 3.0 V under the applied voltage of 9V for Pt/PZT (200 nm 400°C)/PbO (80 nm, 300°C)/Si structures with the PbO buffer layer deposited at the partial pressure of 7:3. From these results, we could assume that the PbO buffer layers play a role of the diffusion barrier between the PZT thin film and the Si substrate as well as the seed layer.

Abstract: For lithium secondary microbattery anode, the tin oxide thin films with the various Si additions (0, 2, 6, 10, 20mol%) were prepared on the p-type (100) SiO2/Si substrate by R.F. magnetron sputtering method at the substrate temperature of 300°C under the gas ratio of Ar/O2 (7/3). The effect of Si addition to the SnO2 thin film on the structural change and electrochemical performance and the reversible capacity performance was investigated. As Si addition amounts increased, Si-O bonding density increased and Sn-O bonding density decreased. The addition of optimum Si amount led decrease of Sn oxidation state so that the irreversible capacity was reduced and cycle characteristic was enhanced during the charge-discharge test. SnO2 films with 6mol%Si had the highest reversible capacity of 700mAh/g after 100cycles.

Abstract: The PZT thin film was deposited by R.F. Magnetron sputtering with Pb 1.1Zr0.53Ti0.47O3 target. When interlayers were inserted at the between PZT and Pt, The grain growth of the PZT thin films was considerably improved by various interlayers (PbO, TiO2, TiO2/PbO) and had low-processing temperature. Compared to the pure PZT thin films, pyroelectric properties of the PZT thin films inserted by interlayers were relatively measured high value. In particular, PZT thin film deposited on interlayer(PbO) was appeared the best pyroelectric properties (P=189.4μ C/㎠K, FD=12.7×10-6Pa-1/2, FV=0.018㎡/C) respectively. As a result of XPS depth profile analysis, both PZT thin film and interlayers were confirmed as independently existing layer respectively.

Abstract: Barium strontium titanate (Ba0.66Sr0.34TiO3) thin films and seed-layers were deposited on the Pt/Ti/SiO2/Si substrate by R.F. magnetron sputtering method. Effects of the substrate temperature on electrical properties of BST thin films were studied. The effect of seed-layer was also studied. From the XRD results, we could confirm that the seeding layer of BST thin film plays a key role in lowering the crystallization temperature of BST thin films. 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.

Abstract: ZrO2 buffer layer and SrBi2Ta2O9 (SBT) thin films were deposited on the P-type Si(111) substrates by the R.F. magnetron-sputtering method. We studied the effect of the post-annealing of the ZrO2 buffer layer on the MFIS structure. We could conclude that the elements of Zr, Sr, Bi, and Ta etc. were diffused by the post-annealing, and according to the process with and without the post-annealing of the ZrO2 layer, the diffusion amount of Sr, Bi, Ta elements shows slight difference through the glow discharge spectrometer (GDS) analysis. From the results of the XPS analysis, we can confirm that a small amount of SiO2 and metallic Zr exist at the interface, and ZrO2 exists as the amorphous state with the weak binding energy before the post-annealing process. Contrarily, after the post-annealing of the ZrO2/Si structure, SiO2 and metallic Zr are observed at the wide range, but the bonding state of ZrO2 is strengthened.

Abstract: The MFS and MFIS structures were prepared on the Si and PbO/Si substrate by the r.f. magnetron sputtering method. When the PbO buffer layer was inserted between the PZT thin film and Si substrate, the crystallization of the PZT thin films was considerably improved, and the processing temperature was lowered. Compared with the MFS structure, memory window values of the MFIS structure with the buffer layer were considerably improved. In particular, in the MFIS structure, the maximum value of the memory window is 2.0 V under the applied voltage of 9V for Pt/PZT (200 nm, 400ı)/PbO (80 nm)/Si structures with the PbO buffer layer deposited at the substrate temperature of 300ı.

Abstract: The SnO2 thin films doped with traces of silicon were deposited on the p-type (100) Si substrate by the r.f. magnetron sputtering method from Sn0.94Si0.06O2 target for the application of lithium secondary micro-battery anode. The crystal orientation of tin oxide thin films was changed from (110) to (101) or (211) with the increase of the substrate temperature. Contrarily, the crystallization of tin oxide thin films, which were heat-treated in the RTA furnace from 450°C to 650 °C under the O2 ambient, did not show significant difference. As a result of the electrochemical analysis, we could see that the irreversible capacity was reduced during the first discharge/charge cycle. Capacity increased with the increase of substrate temperature, but decreased with the increase of RTA temperatures. In particular, the maximum value of reversible capacity was 700mAh/g under the deposition condition of the substrate temperature of 300°C and the Ar:O2 ratio of 7:3.