Improvement of CuAlO₂thin film electrical conduction by the anisotropic conductivity

Abstract

CuAlO2 thin films with (015) preferential orientation growth have been synthesized on quartz substrates using radio frequency (rf) magnetron sputtering at low temperature. Via the optimized postannealing condition (in N2 preserved ambient at 900 °C for 5 h), the preferential orientation of the films changes from (015) to (001) direction. The use of a higher conductivity at the ab plane of CuAlO2 compared with that along the c axis, reduces the resistivity of the film at room temperature to 37 Ω·cm from that of the as-deposited, 4.62 × 104 Ω·cm. The positive Hall coefficient (+183.6 cm3/C) and the large mobility (4.07 cm2/V·s) suggest that CuAlO2 thin films are p-type semiconductors with good conduction path. The temperature dependence of conductivity indicates that CuAlO2 thin films obey a thermal-activation theory when the temperature is above 190 K, but below 185 K a two-dimension variable-range hopping mechanism becomes dominant.

Influence of working gas pressure on structure and properties of CuAlO2 films

“…Thus, it seems that the (0 0 l) preferred orientation is the dominant factor with responsibility for the increase of the Hall mobility and then for the increase of the electrical conductivity with decreasing P W . In our previous paper [22], the hole carrier concentration and Hall mobility are calculated to be around 3.40 Â 10 16 cm À3 and 4.07 cm 2 V À1 s À1 , respectively, which are basically consistent with the results of this work.…”

“…Under the lower P W , the stronger bombardments by higher energetic particles to the substrate surface produce more pits, which increase the nucleation sites. The growth of nuclei along (0 0 l) orientation is much faster than ones along other directions, by which the system has lower energy [22]. It was already reported that the electrical property of CuAlO 2 thin film is anisotropic [22,23].…”

“…The growth of nuclei along (0 0 l) orientation is much faster than ones along other directions, by which the system has lower energy [22]. It was already reported that the electrical property of CuAlO 2 thin film is anisotropic [22,23]. Thus, it is expected to obtain good electrical properties for CuAlO 2 thin films with the (0 0 l) preferred orientation prepared at lower P W .…”

“…Among them, the radio frequency (RF) magnetron sputtering technique shows especially superiority in the large-area deposition techniques and is able to compatible with current microelectronics. Furthermore, the physical properties of sputtered CuAlO 2 thin films are dominated by deposition parameters, such as substrate temperature [16] and oxygen partial pressure [17][18][19]. However, there are scarcely any reports about another important parameter: working gas pressure (P W ), which mianly influences the reactivity, mobility and bombardment of the sputtered atoms during the sputtering process.…”

Preparation and properties of transparent conductive N-doped CuAlO2 films using N2O as the N source

“…were prepared, respectively. After the deposition, all the asprepared films were annealed at 900°C for 5 h in N 2 , the annealing condition had been studied previously [19,20].…”