Scanning Tunneling Microscopy of Semiconductor Surfaces

Kubby, J. A. and Boland, J. J. Scanning tunneling microscopy of semiconductor surfaces. Surface Science Report 26, 61 (1996). 

Two complementary articles related to semiconductor surfaces are Scanning tunnelling microscopy of semiconductor surfaces by H. Neddermeyer, in Rep. Prog. Phys., 59, 701 (1996) and Theory of semiconductor surface reconstruction by G. P. Srivastava, in Rep. Prog. Phys., 60, 561 (1997). The article on scanning tunneling microscopy applied to semiconductor surfaces is replete with pictures of some of the huge variety of surfaces that have been considered in semiconductor systems. 

Neddermeyer, H. (1996) Scanning tunnelling microscopy of semiconductor surfaces. Rep. Prog. Phys., 59, 701-769. 

Ph. Ebert, B. Engels, P. Richard, K. Schroeder, S. Bluegel, C. Domke, M. Heinrich, K. Urban. Contribution of surface resonances to scanning tunneling microscopy images (110) surfaces of III-V semiconductors. Phys Rev Lett 77 2997, 1996. 

The resolution obtained with the laser spot technique is far exceeded by scanning tunneling microscopy where, in some cases, atomic resolution in electrochemical cases has been reached (Szklarczyk and Velev, 1989). The first successful studies of semiconductors in air (Fig. 10.31) and in an electrochemical situation (Fig. 10.32) were made onp-Si 111 (Gonzalez-Martin, 1990). It was found that the electrochemical formation of SiOx and SiOH induces surface states at 0.25 V above the valence band at the surface (Fig. 10.33). 

The development of local probe techniques such as Scanning Tunneling Microscopy (STM) or Atomic Force Microscopy (AFM) and related methods during the past fifteen years (Nobel price for physics 1986 to H. Rohrer and G. Binning) has opened a new window to locally study of interface phenomena on solid state surfaces (metals, semiconductors, superconductors, polymers, ionic conductors, insulators etc.) at an atomic level. The in-situ application of local probe methods in different systems (UHV, gas, or electrochemical conditions) belongs to modem nanotechnology and has two different aspects. 

The general importance of microscopy for surface investigations is reflected in the in situ applications of optical microscopy, scanning tunneling microscopy (STM), and atomic force microscopy (AFM) to oxide and semiconductor electrodes. The methods were described in Chapter 4. Of equal importance for oxide and semiconductor electrodes is the application of ex situ methods like scanning electron microscopy (SEM). 

Electrochemical measurements of the type described earlier give indirect evidence about dissolution processes. More direct chemical information can be obtained from in-situ spectroscopies, in particular from IR and Raman methods. Chazalviel and coworkers have showed the power of this approach in studies on silicon and GaAs [73,98,99]. Electrochemical and spectroscopic techniques are macroscopic methods giving a view of the whole electrode surface. To study semiconductor dissolution at the microscopic (atomic) level, one needs techniques such as scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The anodic and chemical dissolution of sihcon has been studied in very elegant work by Allongue and coworkers [100-102]. 

Figures 5.2-7-5.2-17 give the accepted reconstruction models for a selection of covalent and polar semiconductors, together with STM (scanning tunneling microscopy) images of some of the surfaces. Tables 5.2-6, 5.2-7, and 5.2-8 give the positions of the atoms in reconstructed Si(lll) 2x1 and Si (111)7x7 surfaces and the parameters of the rotation/relaxation model of polar semiconductors.

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