Infrared absorption and slow positron investigation of hydrogen plasma induced platelets in crystalline germanium

N-type germanium samples have been plasma treated which resulted in the formation of hydrogen clusters. It is demonstrated that additional annealing at 600 degrees C forms optical detectable blisters on the surface. To study those hydrogen clusters infrared absorption spectroscopy (IR) and slow positron defect profiling is used. Because the germanium hydrogen stretching mode band clearly consists of distinct bands it can be concluded that different types of clusters have been formed depending on hydrogenation temperature. Two different absorption bands have been observed at 1973 cm(-1) and 2020 cm(-1), which can be assigned to hydrogen clusters involving one and two hydrogen molecules respectively. Although the total hydrogen-germanium bond concentration is higher at lower hydrogenation temperature, it is shown that in terms of percentage more clusters including hydrogen molecules are created at higher hydrogenation temperatures. Slow positron profiling has shown that those defects form up to 300 nm beyond the treated surface.