Electrical and optical properties of phthalocyanine films |
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| Affiliation: | 1. South Kazakhstan State University, Shymkent, Kazakhstan;2. Syrdaria University, Zhetysai, Kazakhstan;3. School of Pharmacy and Pharmaceutical Science, Cardiff University, Cardiff, UK;1. National Centre for Flexible Electronics, Indian Institute of Technology Kanpur, Kanpur 208016, India;2. Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India;1. Technical Physics Division, Bhabha Atomic Research Center, Mumbai 400 085, India;2. Chemistry Division, Bhabha Atomic Research Center, Mumbai 400 085, India;3. Research Reactor Maintenance Division, Bhabha Atomic Research Center, Mumbai 400 085, India;4. Université Paris Diderot, Sorbonne Paris Cité, ITODYS, UMR 7086, CNRS, F-75013 Paris, France;5. Université Paris Est, ICMPE, SPC, PoPI team, UPEC, 2-8 rue Henri Dunant, 94320 Thiais, France;1. Institute of Chemistry, Masaryk University, Kamenice 5, 725 00 Brno, Czech Republic;2. Univ Rennes, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226, Campus de Beaulieu, Rennes Cedex, France;3. Institute of Chemical Process Fundamentals, Czech Academy of Sciences, Rozvojova 135, 165 02 Prague 6, Czech Republic;4. Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, Prague, Czech Republic;5. Department of Electrical and Electronic Technology, Faculty of Electrical Engineering and Communication, Brno University of Technology, Technická 3058/10, 616 00 Brno, Czech Republic;6. Department of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic |
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| Abstract: | Thin films of various phthalocyanines (Pcs) were sublimed onto quartz glass in ultrahigh vacuum. The electrical and optical properties were studied without breaking the ultrahigh vacuum. The dyes were purified by repeated sublimation in vacuum.The conductivity varied with pretreatment (modification) and temperature. Exposure to oxygen, iodine and bromine increased the p-type conductivity by orders of magnitude and lithium doping caused n-type conductivity. Heavy exposure to halogens caused not only broadening of the optical absorption band but also bleaching. Annealing in vacuum removed the electrical and optical effects of doping nearly completely.Field effect studies were used to identify p- and n-type conductivity, to determine the drift mobility and to estimate the trap densities. The field effect and the photoconductivity of p- and n-type films increased by several orders of magnitude with the dark conductivity, i.e. with doping. This correlation is attributed either to traps with a continuous distribution in energy or to trapping by at least two discrete defect levels crossing the Fermi level within the surface-induced accumulation layer. Possible consequences for the sensitivity of semiconductor gas sensors are discussed. |
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