基于接触势差法的表面功函数测试装置

A Novel Instrument for Measurement of Work Function Based on Contact Potential Difference Method

利用接触势差法自行设计开发了一种新型的表面功函数测试装置。基本原理是参考电极与样品之间形成电容,计算流过参考电极与样品之间的电流,通过确定电流的零点来获得功函数。此测量仪器由函数发生、功率放大、振荡器等多个功能模块组成。能在空气环境中快速测量半导体、金属、金属氧化物薄膜的表面功函数。我们运用此装置成功地对有机电致发光的阳极氧化铟锡(ITO)薄膜、p型硅片的功函数进行了测量,得到了样品经过UV-Ozone处理前后功函数随时间变化的曲线,为器件的优化提供了依据。

Work function is an important information for understanding carrier injection in organic electroluminescence. We have made a novel instrument for the measurement of work function using contact potential difference method. The reference tip and sample are used to form a vibrating capacitor. By counting the current between the sample and a reference tip, we found the work function by fixing the zero point of the current. It is mainly composed of signal generator, power amplifier, and oscillator. Signal generator was the signal source of system, it generate sine signal. After magnified by power amplifier, signal was sent to oscillator which can make the reference oscillating. Current between the sample and a reference tip was sent to oscillograph for real-time monitor. At the same time, we apply complement voltage to the surface of sample. By adjusting the complement voltage, we can found the zero point of the current. The instrument can be used to measure the work function of metal, semiconductor and metal-oxide in ambient conditions. This instrument with high practicability and definition is handy to operate, and it can work in ambience. We have measured the work function of p-type silicon （Si） and the thin film of ITO which is used as the anode of organic light emitting devices （OLEDs）. We have set up a relation between work function and time, which shows the change of work function with time. For confirm the practicability of the instrument, we have fabricated two white organic light emitting device with configuration： ITO/CuPc/NPB/TBAND： TPBe： DCJTB/Alq3/Al. We used UV-ITO （ITO treated by UV-Ozone） and ITO without UV for anode of devices. We obtain the current density （J）-vohage （V） character of the devices. It is clear that the performance of devices with UV-ITO is better as the result of the increased work function of ITO. It is useful for the optimization of the devices.