Use of optical fiber pyrometry in molecular beam epitaxy

Abstract

In this work we will present results of experiments using optical fiber pyrometry (OFP) for the measurement and control of temperature in MBE. Examples of substrate temperature measurements using various OFP pyrometry modes will be given and compared to standard optical pyrometry, thermocouple readout, and spectroscopic ellipsometry (SE)). In another example, OFP has been integrated into a standard MBE effusion cell. The OFP measurement is considerably more sensitive than the usual thermocouple used in these applications and can give reproducible temperature resolution of ± 0.01°C at 800°C. This cell design has exhibited long term stability of ± 0.02°C when cell temperatures are controlled by OFP. This is about an order of magnitude better than what is typically available using thermocouples. In addition, because the OFP is measuring light from the crucible it does not depend on thermal contact to an insulator as does a thermocouple. We will present data showing the improved time response possible using the OFP control, in particular short term flux transient response. In addition, we will point out the robustness of the OFP sensor to cell failure modes such as crucible cracking and contamination.