Scanning Microscopy


It has been found that sputter cleaning of GaAs single crystals results in damage or loss of crystallinity in the first few tens of nanometers of the crystal. The damage is a result of both - energetic Ar ions impinging on and being incorporated in the GaAs surface and the resultant preferential sputtering of As from the GaAs lattice. A study of this damage which was done at room temperature and at -110 °C was made by the use of Selected Area Electron Channeling Patterns. The relationship between the degree of surface disorder, as shown by the pattern degradation, and sputtering parameters (ion beam voltage and ion beam dose) was experimentally obtained. The energy regime investigated was 0.5 to 5 keV with sputtering times from 5 to 20 minutes. The results showed increasing contrast degradation in the selected area channeling patterns (SACPs) with increasing incident ion energies from 0.5 to 4 keV, a maxima in contrast degradation for a sputtering time of 10 minutes and greater contrast degradation at room temperature than at -110 °C.

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