A New Time Resolved Electron Spin Resonance with Balanced Double Cavities

在本研究项目中，我们开发了一种新的仪器，以实现时间分辨（TR）ESR（EPR）测量半导体固体，如氧化钛，测量一直是不可能的，直到现在。以前，我们只能观察到极长寿命的自由基形成在半导体表面与CWESR光谱的稳态光照明。在传统的TRESR方法中，由于激光脉冲在半导体固体中形成的短寿命载流子引起介电常数的突变，从而干扰样品腔，降低样品腔的灵敏度（Q值），并由于动态介电变化（DDC）而产生大的瞬态信号。我们使用两个样品腔;一个用于样品，另一个用于参考。利用相位匹配技术，将来自两个谐振腔的两路微波信号在微波电路中混频抵消。样品腔位于外磁场中，外磁场扫描获得TRESR谱。在氧化钛微粒的实验中，我们可以将DDC信号降低到1/%以下，因此总灵敏度提高了约100倍。为了消除腔体不稳定性的影响，增加了外部自动频率控制器（AFC），以获得低噪声信号。到目前为止，该仪器的灵敏度太低，无法成功地测量氧化钛的TRESR，这是我们最初的目的。原则上然而很明显，该方法通常适用于半导体固体，以检测由存在于带隙中的俘获态形成的短寿命顺磁物质。该装置提供了一种新的方法，可普遍用于顺磁中心（缺陷、杂质等）的检测。形成于半导体固体中。

In this research project we have developed a new instrument to realize a time resolved (TR) ESR (EPR) measurement in semiconductor solids such as titanium oxide for which measurement had been impossible until now. Previously, we could only observe extremely long lived radicals formed at the semi-conductor surface with CWESR spectroscopy on steady-state photo illumination. With this new instrument, we will be able to detect a short lived radicals by TRESR In conventional TRESR methods, a sudden change in the dielectric constant, which is induced by short-lived caniers formed on laser pulse in semiconductor solids, disturbs the sample cavities to reduce their sensitivity (Q-value) and to give large transient signals due to the dynamic dielectric change (DDC). We use two sample cavities ; one is for sample and the other is for reference. Two microwave signals coming from either of two cavities are mixed to be cancel out in the microwave circuit by phase matching technique. The sample cavity is located in the external magnetic field which is scanned to obtain TRESR spectra In the experiment with titanium oxide micro particle, we could lower the DDC signal to be less than 1/% and therefore the total sensitivity increased about as 1OO time large as before. We added the extemal automatic tequency controller (AFC) to exclude the effect of instability of cavities to obtain low-noise signal. Until now, the sensitivity of this instrument is too low to succeed in TRESR measurement for titanium oxide which is our initial purpose. In principle. however, it is clear that this method is generally applicable to semiconductor solids to detect short-lived paramagnetic species formed from trapping states existing in the band gap. This apparatus provides a new method which can be generally used for the detection of paramagnetic centers (defects, impurities, etc.) formed in semiconductor solids.