All symbols defined as in Figure 1. is the Schottky barrier height from Equation 3. Three other commonly used metals for metal-assisted etching, all of which can be deposited by galvanic displacement deposition from solution, are Au, Pt, and Pd. These are all high work function metals compared to Si. In all three cases, the bands bend upward. As discussed by Tung [14], the Schottky-Mott relationships are an approximation to the true Schottky barrier height because the presence of surface states, reconstructions, or lack of an abrupt interface can lead to lower www.selleckchem.com/products/mk-5108-vx-689.html values. This is corroborated by comparison of the experimental values on n-type Si to the calculated values

in Table 1. The values for Ag are close to the ideal value. In all other cases, interfacial chemical and structural changes reduce the barriers below the ideal values. However, the shape of the band bending is always correctly predicted by the Schottky-Mott

relations. Therefore, they can be used to characterize the qualitative shape of the bands at the interface, and deviations from ideal character will not be important for hole injection into the valence band as discussed below. It is not the Schottky barrier itself that is of interest; rather, it is band bending and the energy of the Si valance band at the interface that are important. This is because a hole must be transferred from the metal to the Selleck BKM120 Si valence band to induce etching. The Schottky-Mott analysis allows us to calculate the energy of the Si valence band maximum at the interface, which is labeled E in Figures 1 and 2. Holes naturally relax to the highest available energy in a band, whereas electrons relax to the lowest energy in the band. The definition of the Schottky barrier height is the energy required to move a charge carrier from the metal to the Si interface; however, the carrier clonidine changes from www.selleckchem.com/products/bay-1895344.html p-type to n-type Si. On p-type material, the Schottky barrier height is the energy required to move a hole from

the metal to the Si valence band at the interface. Therefore, the Schottky barrier height is the same as the energy of the Si valence band maximum at the interface. On n-type material, the Schottky barrier height is the energy required to move a hole from the Si conduction band at the interface to the metal. This value is not directly relevant to the discussion of etching. Rather, it is again the energy of the Si valence band maximum at the interface E that is required. A nonideal interface may introduce gap states between the conduction and valence bands, which affects the Schottky barrier height. However, the introduction of gap states does not change E. Therefore, any inaccuracies in the Schottky-Mott relationships will not change the direction of band bending and should not affect the conclusions of the model presented here. Figures 1 and 2 show that Ag is clearly different than all other metals.