In-situ monitoring by reflective high energy electron diffraction during pulsed laser deposition

Pulsed laser deposition PLD.has developed during the past decade from a fast but limited preparation tool towards a competitive thin film deposition technique. One of the advantages above other techniques is the possibility of growth at relative high background pressure. There is a large freedom in choosing which kind of gas. Moreover, in a number of applications, the gaseous species in the background pressure are part of the elements to be grown, e.g., oxygen in the case of high Tc superconductors. However, the advantage of relative high pressures leads to restrictions of using standard diagnostics and monitoring of the film growth, e.g., reflective high energy electron diffraction RHEED.. Here, a PLD chamber including an in-situ RHEED system is presented, which makes it possible to monitor and study the growth at standard PLD parameters. Using a two-stages differential pumped, magnetically shielded, extension tube mounted at the electron gun side and a special designed phosphor screen including CCD camera, real time monitoring by observation of RHEED oscillations could be established at pressures up to 50 Pa. In this paper the latest results on applying this technique on SrTiO3and YBa2Cu3O7 will be presented. Additional to the usual diagnostics performed with RHEED, another phenomena can be observed. The pulsed way of deposition, characteristic for PLD, leads to relaxations in the intensity of the diffracted pattern due to the mobility of the deposited material. These relaxation times give extra information about relaxation, crystallization, and nucleation of the deposited material. The presented technique leads to a better understanding of the growth during pulsed laser deposition and, because of the possibility to monitor the growth, will make PLD competitive with other deposition techniques. q1999 Published by Elsevier Science B.V. All rights reserved.