Exploring Charge Transfer Dynamics in RuCl₃/hBN/WSe₂ Heterostructures
Introduction
During my time as an undergraduate researcher at the University of California, Berkeley, I had the opportunity to delve into the study of charge transfer dynamics in RuCl₃/hBN/WSe₂ heterostructures. This project not only enhanced my understanding of two-dimensional (2D) materials and their interfaces but also allowed me to acquire a range of experimental skills in device fabrication and optical measurements.
1. Preparation of Two-Dimensional Material Flakes
The foundation of our research relied on high-quality flakes of various 2D materials:
- Graphene
- Hexagonal Boron Nitride (hBN)
- Tungsten Diselenide (WSe₂)
- Ruthenium Trichloride (RuCl₃)
I learned to prepare these flakes using mechanical exfoliation techniques. This process involves peeling thin layers from bulk crystals using adhesive tapes and transferring them onto substrates for further processing. Mastery of this technique was crucial for obtaining flakes with the desired thickness and purity. Additionally, I developed a neural network to efficiently identify thin hBN flakes, significantly accelerating the progression to device fabrication.
2. Fabrication of RuCl₃/hBN/WSe₂ Heterostructure Devices
I was introduced to the polyethylene terephthalate (PET) transfer technique, which allowed for precise stacking of 2D materials. Given RuCl₃’s sensitivity to moisture, I learned to perform part of the fabrication process within a glove box under an inert atmosphere.
Structure of the device
Transfer Stage and Glove Box Used in this project
I learned how to perform photolithography to create patterns for electrical contacts. Additionally, I was trained in thermal evaporation techniques to deposit gold electrodes onto the device.
Photolithography process for device fabrication
All the devices I fabricated are shown in the image below.
Fabricated devices with absorption spectra for selected samples
3. Optical Measurements and Data Collection
I learned how to perform absorption spectroscopy measurements to evaluate the quality of the fabricated devices. All non-leaking devices I produced underwent this assessment. The absorption spectra provided valuable insights into the optical properties of the heterostructures and helped determine their suitability for further experiments.
Conducting measurements with Jingxu in the laboratory
In addition to absorption spectroscopy, I assisted Jingxu with pump-probe measurements and lock-in detection methods for other projects.
Data analysis of lock-in measurements showing polarization angle variations at different device locations
These measurement experiences significantly enhanced my skills in data collection and analysis, providing a comprehensive view of the experimental process in materials research.
Conclusion
This research experience at UC Berkeley has been incredibly enriching, allowing me to develop a wide range of skills in nanofabrication and advanced measurement techniques. I learned to prepare and identify 2D material flakes, fabricate complex heterostructures, and conduct various optical measurements.
The hands-on experience in device fabrication, from exfoliation to photolithography and electrode deposition, has given me a deep appreciation for the intricacies of experimental physics. Learning to perform absorption spectroscopy, pump-probe measurements, and lock-in detection has significantly enhanced my understanding of material characterization methods.
This project has not only improved my technical skills but also strengthened my problem-solving abilities and scientific curiosity. It has solidified my interest in condensed matter physics and motivated me to pursue further research in this field. I am grateful for this opportunity and look forward to applying these skills in future scientific endeavors.