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Work Functions and Injection Barriers
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
Photoelectron spectroscopies (PES) consist of a range of methods in which electrons in a solid are excited by high-energy photons. Carriers excited above the SVL abandon the material with certain kinetic energy, and the resulting spectrum of photoelectrons as a function of the kinetic energy is measured in a detector. These methods provide a detailed picture of electronic states in the material from the Fermi level downward. In Inverse Photoemission Spectroscopy (IPES) incident, electrons with controlled kinetic energy (5–15 eV) penetrate the solid above the VL and decay in an empty state. The decay of the electron produces a photon that is recorded by the detector. The IPES provides a view of the unoccupied electronic states of the conduction band.
Oxidation behavior with quantum dots formation from amorphous GaAs thin films
Published in Philosophical Magazine, 2018
Srikanta Palei, Bhaskar Parida, Keunjoo Kim
Microtextured crystalline p-type Si(100) wafers with a thickness of 200 μm, resistivity of 0.5–3.0 Ω-cm, and size of (6 in × 6 in) were used for thin film deposition of amorphous GaAs layer. A further nanotexturing process was carried out on the microtextured wafer by conventional two-step Ag-metal-assisted chemical etching. The detailed procedure of the nanotexturing process is available in our previous studies [21,22]. We deposited an amorphous GaAs thin film onto the micro/nanotextured Si surface by an electron-beam (E-beam) evaporation process (Duksung system). The Si-doped n-GaAs(100) wafer with a carrier concentration of (1.4–3.96) × 1018/cm3 was used as the beam target in a high-vacuum chamber under a pressure of approximately 1.0 × 10−7 Torr. The deposition was carried out for 20 min, and the conditions for electron emission were: emission current of 20 mA, a voltage of 2.8 kV, and a deposition rate of 10 nm/min. Short-term (2 days) and long-term (2 months) air-exposed amorphous GaAs thin films were analyzed by field-emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), inverse photoemission spectroscopy (IPS), and photoluminescence (PL) measurement. Furthermore, dark current-voltage (I-V) characteristics of samples were measured for analyzing the tunnelling phenomenon.