tailieunhanh - Topological insulator Bi2Te3 films synthesized by metal organic chemical

Using chemical ionization mass spectrometry and photo- acoustic spectroscopy, we analysed the evolution of vola- tile organic compounds (VOCs) and other trace gases dur- ing an approximately one-week measurement period each in a pigsty and a sheep shed at the Federal Agricultural Research Centre (FAL) in Mariensee, Germany. When ac- tivities in the sheep shed were most intense during feeding hours and manure removal, concentration surges of VOCs were observed, which strongly correlated with methane and ammonia levels. Immediately after this disturbance, especially the manure removal, which lasted for about 30 minutes, the short-term concentration spikes decayed exponentially as a result of dilution of. | Topological insulator Bi2Te3 films synthesized by metal organic chemical vapor deposition Helin Cao1 2 Rama Venkatasubramanian3 Chang Liu4 5 Jonathan Pierce3 Haoran Yang6 M. Zahid Hasan4 5 Yue Wu6 Yong P. Chen1 2 7 1Physics department Purdue University West Lafayette IN 47907 2Birck Nanotechnology Center Purdue University West Lafayette IN 47907 3Center for Solid State Energetics RTI International Research Triangle Park NC 27709 Joseph Henry Laboratories Department of Physics Princeton University Princeton New Jersey 08544 USA 5Princeton Institute for Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA 6School of Chemical Engineering Purdue University West Lafayette Indiana 47907 7School of Electrical and Computer Engineering Purdue University West Lafayette IN 47907 Emails rama@ yongchen@ Abstract Topological insulator TI materials such as Bi2Te3 and Bi2Se3 have attracted strong recent interests. Large scale high quality TI thin films are important for developing TI-based device applications. In this work structural and electronic properties of Bi2Te3 thin films deposited by metal organic chemical vapor deposition MOCVD on GaAs 001 substrates were characterized via X-ray diffraction XRD Raman spectroscopy angle-resolved photoemission spectroscopy ARPES and electronic transport measurements. The characteristic topological surface states SS with a single Dirac cone have been clearly revealed in the electronic band structure measured by ARPES confirming the TI nature of the MOCVD Bi2Te3 films. Resistivity and Hall effect measurements have demonstrated relatively high bulk carrier mobility of 350 cm2 Vs at 300K and 7 400 cm2 Vs at 15 K. We have also measured the Seebeck coefficient of the films. Our demonstration of high quality topological insulator films grown by a simple and scalable method is of interests for both fundamental research and practical applications of thermoelectric and TI materials. For decades .