Time-and space-resolved study on the effect of high-density excitation in ion tracks

我们的快速衰变测量技术-单离子和单光子符合(SISP)得到了进一步的发展，获得了85ps的分辨率(迄今为止报道的同类设备中最快的离子辐照)，并获得了时间分辨光谱。针对其在不同领域的应用，将SISP型探测器安装到TOF系统中，开发了一种新的杂质分析系统。我们的结果如下：在离子辐照的氧化铝晶体中发现了一个新的超短寿命发光带，这是激光和脉冲电子辐照所没有的。该带在340 nm附近有一个峰值，带宽为2 eV，短寿命为100ps。进一步的实验表明，在氧化物、碱金属和碱土卤化物等多种晶体中都能观察到新的谱带。考虑到结果所表现出的对激发密度的超线性依赖性、温度无关性、超短寿命和宽带特性，可以得出这样的结论：由电子-空穴对和其他激发态组成的电子-空穴等离子体或复合体已经形成。由于电子-空穴等离子体的弛豫发光，我们指定了这个新的谱带。这一发现可能开启和引领离子辐照效应的研究进入新的发展阶段，并使研究高密度激发和宽禁带晶体的等离子体效应成为可能。

Our technique for fast decay measurements-single ion and single photon coincidence(SISP) was further developed to obtain a resolution of 85 ps (the fastest of the similar equipment's reported for ion irradiation so far) and also to take a time-resolved spectrum. As for its application to different fields, a detector of the SISP was installed into a TOF system and a new impurity analysis system was developed. Our results ale as follows.A new ultra-short lived luminescence band was found in ion irradiated alumina crystals, which has not been found by laser and pulsed electron irradiation. This band has a peak around 340 nm a broad band-width of 2eV, and a short lifetime of 100 ps. Further experiments elucidated that the new band could be observed in a many kind of crystals like oxides, alkali and alkali-earth halides. Considering characteristics shown by the results, the super-linear dependence on excitation density, the temperature independence, a ultra short lifetime, and a broad band, it may be concluded that the electron-hole plasmas or complexes composed of the electron-hole pair and other excited states are formed. We assigned this new band due to luminescence associated with the relaxation of the electron-hole plasma. This finding may open and lead the study for ion-irradiation effects into new development and also make it possible to study the effect of high-density excitation and the plasma of the wide band-gap crystals.