DC-electric-field effect on CdSe nanocrystal embedded in Indium tin oxide film and its second-order nonlinearity
DC-electric-field effect on CdSe nanocrystal embedded in Indium tin oxide film and its second-order nonlinearity
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氧化铟锡薄膜中CdSe纳米晶的直流电场效应及其二阶非线性
DOI：
10.1016/s1359-6462(01)00688-1
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发表时间：
2001
影响因子：
6
通讯作者：
N. Koshizaki
中科院分区：
文献类型：
--
作者：
A. Narazaki;T. Hirano;Jun Sasai;Katsuhisa Tanaka;K. Hirao;T. Sasaki;N. Koshizaki
研究了直流电场对射频法制备的非晶氧化铟锡（ITO）薄膜中镶嵌的CdSe纳米晶的晶体生长和二阶非线性光学性能的影响。研究了溅射。沉积态薄膜的电流-电压曲线表现出共同的特征;随着电压的升高，电流遵循欧姆定律增加，并在36 V/cm附近突然下降。当样品通过施加50 V/cm的直流电场进行电处理时，CdSe纳米晶以初始取向保持不变的方式生长，如X射线衍射图案所示。考虑到处理过程中样品表面温度升高至250°C，晶体生长是由于焦耳热导致温度升高而发生的。另一方面，当沉积的薄膜在不施加电压的情况下进行热处理时，CdSe微晶以随机取向生长，伴随着ITO基质在400°C下的结晶。从电处理和热处理的薄膜之间的结晶平衡的差异，我们推断，在电处理的薄膜中的优先晶体生长的CdSe可以归因于电场以及焦耳热。电处理薄膜的二次谐波强度比沉积薄膜提高了两个数量级，是热处理样品的两倍。
The effect of DC-electric-field on crystal-growth and second-order nonlinearity of CdSe nanocrystals embedded in amorphous indium tin oxide (ITO) films prepared by r.f. sputtering has been investigated. The current-voltage curves of the as-deposited films exhibit common characteristics; with raising voltage the current increases following the Ohmic law, and shows an abrupt decrease at around 36 V/cm. When samples were electrically-treated by applying a DC electric field of 50 V/cm, CdSe nanocrystals grew with the initial orientation kept unchanged as indicated by the X-ray diffraction patterns. Considering the fact that temperature of the sample surface was raised up to 250°C during the treatment, the crystal-growth occurred as a result of an increase in temperature due to the Joule heat. On the other hand, when the as-deposited films were heat-treated without applying voltage, CdSe crystallites grew with random orientations, accompanied by crystallization of ITO matrix at 400°C. From the difference in crystallization bahavior between the electrically- and heat-treated films, we infer that the preferential crystal-growth of CdSe in the electrically-treated film can be attributed to the electric field as well as the Joule heat. The second-harmonic intensity for the electrically-treated films was enhanced by two orders of magnitude compared with the as-deposited films and was twice as large as that of the heat-treated samples.