Integration of a Raman spectroscopy system with a low-temperature scanning tunnelling microscope under UHV conditions

Abstract

This article presents an optical system for integrating Raman spectroscopy with a commercial low-temperature scanning tunnelling microscope (LT-STM) operating under ultrahigh vacuum (UHV) conditions. The external excitation, collection, filtering, alignment and mechanical-support modules were designed and constructed to match the factory-defined 30° optical geometry of the LT-STM platform while avoiding direct mechanical modification of the suspended STM head. The performance of the integrated configuration was evaluated at room temperature using a single-crystal silicon reference sample and compared with a near-normal-incidence Raman configuration operated in a glove-box environment. Analysis of 100 individual acquisitions per configuration showed low short-term acquisition-to-acquisition variability. After normalisation to the incident excitation power measured immediately before the corresponding external window, the mean integrated intensity of the first-order silicon Raman band in the LT-STM configuration was lower than that obtained in the glove-box configuration by a factor of approximately 7.4. The first-order silicon phonon band remained clearly resolved in the LT-STM configuration. The results demonstrate the feasibility of far-field Raman detection under UHV conditions and provide a practical basis for future low-temperature Raman and TERS studies.