제주장학재단

In reflection high-energy electron diffraction (RHEED,) a high energy (20-30 keV) electron beam is incident on the film growth surface at a glancing angle of ~2˚- 5˚. The diffraction pattern created on a screen contains information about the crystal structure of the film, stress at the interface, possible impurity phases etc and can be used for real-time monitoring of the film quality. The RHEED oscillations, where the RHEED specular spot intensity is monitored as a function of deposition time provides information on the deposition rate as well as information on the growth mode (2D vs 3D) of the deposited film. A high quality 2D layer-by-layer growth mode is inferred by the observed RHEED intensity oscillations extending to several cycles. Double differential pumping of the RHEED source facilitates high-pressure operation up to about 500 mTorr, facilitating real-time monitoring of complex oxide film growth at high oxygen pressures.

High-pressure RHEED systems are routinely integrated with Neocera PLD systems, but can also be integrated with existing PLD systems. It is however mandatory, that the deposition system should have ports for both the RHEED gun and the RHEED screen at an optimal position with respect to the substrate surface. Care is also required for providing customer-safety from harmful X-rays. The essential components of a high-pressure RHEED system are (1) RHEED electron gun and RHEED screen, (2) double differential pumping system and accessories for high-pressure operation and (3) a high-sensitivity CCD camera for image processing and (4) data acquisition software for analysis.