Electrical Characterization and Metal Contacts of ZnO Thin Films Grown by the PLD Method

In this study, metal/ZnO contacts were thermally annealed at different temperatures (as-dep., 400$^{\circ}C$, 600$^{\circ}C$, 800$^{\circ}C$, 1000$^{\circ}C$) for the investigation of electrical properties, and surface and interface characteristics. The analysis of the element composition and the chemical bonding state of the surface was made by the XPS(X-ray photoelectron spectroscopy). An attempt was made to establish the electrical property-microstructure relationship for the (Ti, Au)/ZnO. The Ti/ZnO contact exhibits an ohmic characteristics with a relatively high contact resistance of 4.74${\times}$10$\^$-1/ $\Omega$$\textrm{cm}^2$ after an annealing at 400$^{\circ}C$. The contact showed a schottky characteristics when the samples were annealed at higher temperature than 400$^{\circ}C$. The transition from the ohmic to schottky characteristics was contributed from the formation of the oxide layers as was confirmed by the peaks for O-O and Ti-O bondings in XPS analysis. For the Au/ZnO contact the lowest contact resistance was obtained from the as-deposited sample. The resistance was slowly increased with annealing temperature up to 600$^{\circ}C$. The ohmic characteristics were maintained eden fort 600$^{\circ}C$ annealing. The XPS analysis showed that the Au-O intensity was dramatically decreased with temperature above 600$^{\circ}C$.

PLD 방법에 의해서 증착된 ZnO 박막의 전기적 특성 및 접합 특성에 관한 연구