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Synchrotron radiation photoemission spectroscopy is used for measuring the work functions of CdZnTe single crystal with different surface states. The relationship between work function, surface dipole, valence band bending, ionization energy and electron affinity of CdZnTe with different surface states are discussed.

The clean and ordered surfaces of CdZnTe (111)B grown by the Bridgman method were obtained by Ar ion bombardment and thermal annealing in situ in an ultrahigh vacuum. The surface atomic structures of CdZnTe (111)B after annealing at different temperature were observed by low-energy electron diffraction (LEED). The valence band and work function of CdZnTe (111)B surfaces were determined by synchrotron radiation photoemission spectroscopy. The order of CdZnTe (111)B after annealing at 350 °C will worsen, and the (111)B-(2 x 2) local reconstruction will be formed. The work function of CdZnTe (111)B after annealing at 350 °C is 0.8 eV higher than that of CdZnTe (111)B-(1 x 1), and the local reconstruction may be induced by Te adatoms on top of the ideal truncation [ABSTRACT FROM AUTHOR]

Layered materials, such as graphite/graphene, boron nitride, transition metal dichalcogenides, represent materials in which reduced size, dimensionality, and symmetry play critical roles in their physical properties. Here, we report on a comprehensive investigation of the phonon properties in the topological insulator Bi2Te3 and Bi2Se3 two-dimensional (2D) crystals, with the combination of Raman spectroscopy, first-principles calculations, and group theory analysis. Low frequency (<30cm-1) interlayer vibrational modes are revealed in few-quintuple-layer (QL) Bi2Te3/Bi2Se3 2D crystals, which are absent in the bulk crystal as a result of different symmetries. The experimentally observed interlayer shear and breathing mode frequencies both show blueshifts, with decreasing thickness in few-QL Bi2Te3 (down to 2QL) and Bi2Se3 (down to 1QL), in agreement with first-principles calculations and a linear chain model, from which the interlayer coupling force constants can be estimated. Besides, an intense ultralow (<12cm-1) frequency peak is observed in 2-4QL Bi2Te3, which is tentatively attributed to a substrate-induced interface mode supported by a linear chain model analysis. The high frequency Raman peaks exhibit frequency shifts and broadening from 3D to 2D as a result of the phonon confinement effect. Our studies shed light on a general understanding of the influence of dimensionality and crystal symmetry on the phonon properties in layered materials. [ABSTRACT FROM AUTHOR]