1. 연수기간 : 2021. 11. 21 ~ 2021. 11. 25 (총 4박 5일)
2. 연수국가 : 온라인 진행
3. 연수기관명 : KVS (The Korean Vacuum Society)
4. 연수자 : 석박사통합과정 6기 참여대학원생 1명
5. 연수주제 : Electrical Properties and Structure Transition of Tetragonal Polymeric C60 Under High Pressure
C60 is known to form polymer or dimer between fullerene cages under high pressure and temperature.Two-dimensional tetragonal polymeric C60 is predicted to transform to a three-dimensional metallic polymer under uniaxial compression of about 20 GPa [1]. In this work the electrical properties and structure of two-dimensional tetragonal polymeric C60 were studied under high uniaxial pressure up to 30.8 GPa to investigate the phase transformation.The electrical resistance value, R, decreased from 1010 to 5*105 Ω as a result of pressure cycling (with ramp pressure increase in each cycle) to a maximum pressure of 30.8 GPa by using a diamond anvil cell (DAC). A substantial drop in R after decompression (107 Ω) was reached in a cycle with a ramp pressure of 22 GPa that we consider as a cross-over/phase transition p. A subsequent p-cycling to 30.8 GPa resulted in further (20 times!) drop in the R of the recovered sample and exhibited anomalies in R vs p behavior. The results of Raman measured after decompression showed that the ratio of the 2-dimensional tetragonal (T) phase to 1-dimensional orthorhombic (O) phase decreased as increasing the cycling pressure. Raman-mapping of the recovered material showed Raman spectra inhomogeneity across the sample stemming from a non-hydrostatic pressure distribution in the DACs and the relationship between shear and normal stress. The details of phase transition pathways combining with the results of XRD will be presented.
1. Okada, S., S. Saito, and A. Oshiyama, New metallic crystalline carbon: three dimensionally polymerized C60 fullerite. Physical review letters, 1999. 83(10): p. 1986.