Low Temperature Scanning Tunneling Microscope with Improved Head Design and Its Application to The Study of Bi2Sr2CaCu2O8+x Single Crystal

Abstract

Low Temperature Scanning Tunneling Microscopy (LT-STM) is a valuable tool not only in surface science but also, in condensed matter physics. Here, we present three improvements in Ultra Low Vibration (ULV) Lab and LT-STM design : tip treatment stage, sample cleaving stage and vibration isolation system. Improved tip treatment stage enables us to perform field emission for a tip treatment in-situ without exchanging samples, while our enhanced sample cleaving stage allows us to cleave samples at low temperature in vacuum without optical access by a simple pressing motion. Our newly designed vibration isolation system provides an efficient space usage while maintaining a vibration isolation capability. These improvements enhance the quality of spectroscopic imaging experiment which can last for many days and also provide an increased data yield. On the other hand, since Nanonis STMTM (Generic4) controller comes with basic default sets of functions while it lends an expendability in its functionality via LabviewTM, we added additional customized protocols for our experimental method of choice : Spectroscopic Imaging STM (SI-STM). In addition, since the library of analysis tools accumulated over decades for an outdated topometrixTM STM controller is vast and comprehensive, we choose to write a C++ protocol which can convert raw data form at from Nanonis to a data form at which is compatable with already existing such analysis programs rather than creating entire analysis library from the scratch. Finally, we demonstrated SI-STM performances at 4K on highly overdoped Bi2Sr2CaCu2O8+x using ULV Lab facility which is much more compact than conventional ULV Lab design. In this thesis, I will describe such improvements in STM instrumentations as well as in softwares for STM controls and data analysis.