X-Ray Diffractometer for Studies on Molecular-Beam-Epitaxy Growth of III–V Semiconductors

An X-ray diffractometer connected with a molecular-beam epitaxy (MBE) system has been constructed for in situ studies on the growing surfaces of III–V compound semiconductors. This diffractometer is based on the (4+2) type, which has four axes for orienting the sample and two axes for positioning the detector. In addition, it is equipped with an axis for rotating the receiving slit about the normal of the slit plane to align the resolution of the receiving slit properly for the surface X-ray diffraction measurement. For the alignment of the sample and the entire setup with respect to the X-ray beam, an XYZ-stage and an adjustable base plate are available. X-rays enter and leave the chamber through two Be windows welded directly to the MBE chamber. A graphite sheet which can be heated up to 250°C is placed along the inside of the Be windows to protect the Be windows from being coated with evaporated materials. Preliminary data are presented to demonstrate the feasibility of static and dynamic measurements of growing surfaces using this instrument.