热电Ca3Co4O9薄膜的一致取向生长及其激光感生电压效应

Growth and Laser Induced Thermoelectric Voltages Effect of the c-Axis Oriented Thermoelectric Ca_3Co_4O_9 Thin Films on Sapphire Substrates

利用脉冲激光沉积(PLD)法,在蓝宝石(0001)平衬底上成功制备了c轴一致取向的Ca3Co4O9薄膜。利用X射线衍射(XRD)分析测定了薄膜的相结构和生长取向。研究了不同衬底温度与不同原位氧压对Ca3Co4O9薄膜结晶质量与生长取向的影响,确定了最佳生长条件。利用这一条件在倾斜Al2O3(0001)衬底上制备了Ca3Co4O9薄膜。研究发现,当Ca3Co4O9薄膜被波长248nm,脉冲宽度20ns的脉冲激光照射时,在薄膜两端存在较大的激光感生热电电压(LITV)信号,峰值电压达到4.4V,其上升沿为36ns,半峰全宽(FWHM)为131ns。可以认为这种激光感生热电电压信号是由于Ca3Co4O9薄膜面内与面间泽贝克(Seebeck)系数张量的各向异性引起的。

The c-axis oriented thermoelectric Ca3Co4O9 thin films were prepared on sapphire （0001） substrates using pulsed laser deposition （PLD） technology. X-ray diffraction （XRD） was used to determine the micro-structure and orientation of Ca3Co4O9 thin films. The influence of substrate temperature and oxygen pressure on crystalline and orientation of thin films was investigated and the optimal conditions were determined. Optimal conditions were used to prepare Ca3Co4O9 thin films on vicinal-cut Al2O3 （0001） substrates. When the Ca3Co4O9 film was irridated by laser with wavelength of 248 nm, pu/se bandwidth of 20 ns, the two ends of the film would induce thermoelectric voltages （LITV）. And the peak voltage and response time at the two ends of the film can reach 4.4 V and 36 ns respectively. And the bandwidth of the voltage is 131 ns. The correlated mechanism of this phenomenon was discussed.