Abstract
Tin monosulfide (SnS) is a naturally p-type semiconductor with a layered crystal structure, but no reliable n-type SnS has been obtained by conventional aliovalent ion substitution. In this work, carrier polarity conversion to n-type was achieved by isovalent ion substitution for polycrystalline SnS thin films on glass substrates. Substituting Pb2+ for Sn2+ converted the majority carrier from hole to electron, and the free electron density ranged from 1012 to 1015 cm−3 with the largest electron mobility of 7.0 cm2/(Vs). The n-type conduction was confirmed further by the position of the Fermi level (EF) based on photoemission spectroscopy and electrical characteristics of pn heterojunctions. Density functional theory calculations reveal that the Pb substitution invokes a geometrical size effect that enlarges the interlayer distance and subsequently reduces the formation energies of Sn and Pb interstitials, which results in the electron doping.
Highlights
This way of thinking would provide more flexibility to explore new doping routes, open a new way for controlling carrier polarity and density in novel semiconductors in which conventional aliovalent ion substitution is difficult
The crystalline phase and crystal structure of the obtained films were characterized by X-ray diffraction (XRD, radiation source = Cu Kα )
The Pb content in the films were determined by X-ray fluorescence (XRF) spectroscopy calibrated by the chemical compositions obtained by inductively-coupled plasma-atomic emission spectroscopy (ICP-AES)
Summary
This way of thinking would provide more flexibility to explore new doping routes, open a new way for controlling carrier polarity and density in novel semiconductors in which conventional aliovalent ion substitution is difficult. Sn1−x f Pbx f S films of 100–200 nm in thickness were grown on SiO2 glass substrates by pulsed laser deposition (PLD) using a KrF excimer laser ( ) laser flow energy density, and 10 Hz of repetition rate) with to control the S stoichiometry. Sn1−xtPbxt S polycrystalline of the growth chamber was targets in a H2S 1 × 10−5 Pa. Ts gas was varied from 200 to 400 °C, and P of an Ar/H2S mixing gas (80/20%) from 5 to 20 Pa. Characterization.
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