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Development of field-assisted photochromism and an application to an optical memeory

场辅助光致变色的发展及其在光学存储器中的应用

基本信息

批准号：
09555194
负责人：
KOBAYASHI Kenkichiro
金额：
$ 5.12万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

A four-layer device of ITO/Cu-ZnS/SiO_2/metal was fabricated by a sputtering technique ITO/Cu-ZnS/SiO_2/Al devices exhibits low leakage current at an applied voltage of 70 V (an electric filed of 10^8 V/cm). Transient photocurrent at 700 nm is observed only after irradiation of 400 nm. However, no change of absorbance is detected after irradiation of 700 or 400 nm. The reason is that SiO_2 film prevents the charge transfer between Al and Cu-ZnS under light irradiation. Then, we adopted AlN as a host material because AlN has a wide band gap and a considerable hole mobility. AlN films were prepared by RF reactive sputtering technique. Crystalline AlN films were prepared on sapphire substrates under RF power of 100 W or more. C-axis oriented AlN films were deposited on quart and ITO films at a substrate temperate higher than 300℃. The electrical properties of ITO/AlN/Al devices arc dependent on the substrate temperature in the process of deposition of AlN film. No leakage current was observed at 70 Vor less when AlN film in the ITO/AlN/Al device as deposited at 700 ℃. Continuous photocurrent flows at wavelength < 400 nm, and a peak is seen at 280 nm in the spectra of photocurrent. Magnitude of photocurrent is independent of the polarity of a bias voltage, and thus the photocurrent is originated from the photo-induced charge transfer between deep levels and conduction (or valence) bands of AlN.Optical absorbance of the device decreases after the irradiation of 280 nm, and is recovered to the intial value after the irradiation of 380 nm. The change in the optical absorbance is maintained for a few days in the presence of an electric field. These results suggest that the field-assisted photochromism is a powerful method as an optical memory.

采用溅射技术制备了ITO/Cu-ZnS/SiO_2/金属四层器件。ITO/Cu-ZnS/SiO_2/Al器件在施加电压为70 V（电场为10^8 V/cm）时具有较低的漏电流。在700 nm处的瞬时光电流只有在400 nm照射后才能观察到。而在700 nm和400 nm照射后，吸光度没有变化。原因是SiO_2薄膜在光照射下阻止了Al和Cu-ZnS之间的电荷转移。然后，我们采用AlN作为宿主材料，因为AlN具有较宽的带隙和相当大的空穴迁移率。采用射频反应溅射技术制备了AlN薄膜。在100 W以上的射频功率下，在蓝宝石衬底上制备了晶体AlN薄膜。在衬底温度高于300℃的条件下，在夸脱和ITO薄膜上沉积了c轴取向AlN薄膜。在AlN薄膜沉积过程中，ITO/AlN/Al器件的电学性能与衬底温度有关。当ITO/AlN/Al器件中的AlN膜在700℃下沉积时，在70℃以下未观察到漏电流。光电流在< 400 nm处连续流动，光电流光谱在280 nm处出现峰值。光电流的大小与偏置电压的极性无关，因此光电流源于AlN的深能级和导（价）带之间的光诱导电荷转移。器件的光吸光度在280 nm照射后降低，在380 nm照射后恢复到初始值。在电场的作用下，光学吸光度的变化可以维持几天。这些结果表明，场辅助光致变色是一种强有力的光存储器方法。