脉冲激光沉积中高能量密度激光密度对Cu_2Se热电薄膜成分与性能的影响

Congruent Growth of Cu_(2)Se Thermoelectric Thin Films Enabled by Using High Ablation Fluence During Pulsed Laser Deposition

本工作提出了脉冲激光沉积法生长Cu2Se热电材料薄膜中维持较高的激光切削能量密度对于实现薄膜与靶材成分等比例传输的重要性。使用较高的脉冲激光能量生长的Cu2Se薄膜具有纯的?-相,并具有与靶材相近的化学组分。这主要是因为较高的激光能量可以更加有效地引起等离子体对激光-固体直接作用的屏蔽,这可以使得靶材中的铜和硒元素的激光切削量更加接近靶材的化学计量比。由于硒具有较高的蒸汽压,降低激光能量会加强激光与固体的直接作用,从而更有效地切削硒元素,导致所沉积薄膜中产生铜缺陷。进一步讨论了所使用的氩气背景气体压力对于所生长的Cu2Se薄膜热电性能的影响。当使用高激光能量低背景气体压力时,所生长的薄膜具有最佳的热电性能。

The importance of the laser ablation fluence in congruent growth of Cu2 Se thermoelectric thin films during pulsed laser deposition was shown in this work. By using a larger laser ablation fluence, a more consistent composition between as-grown thin films and the target material has been realized in the pulsed laser deposition of Cu2 Se films. This is associated with the enhanced plasma shielding effect, which weakens direct laser-solid interaction when increasing laser fluence. Reducing the ablation fluence can obviously increase the amount of the copper deficiencies, due to more effective laser ablation of Se（higher vapor pressure） than that of Cu when the laser direct lasser-solid interaction becomes more efficient. Apart from tuning the ablation fluence, thermoelectric performances of as-grown Cu2 Se thin films are further optimized as a function of the used argon background gas pressures. The maximum thermoelectric performance of the Cu2 Se thin film can be obtained when using the highest ablation fluence（～10 J/cm^2） and a low argon background pressure（～10^-1 Pa）.