Etching behavior

Khanna et al. [136] proposed a mechanism of the reactions of aluminum based clusters with O, which lends a physical interpretation as to why the HOMO-LUMO gap of the clusters successfully predicts the oxygen etching behaviors. The importance of the HOMO-LUMO gap strongly suggests that the reactions of the metal clusters belong to the pseudoexcitation band. 

Refractive index measurements made by this technique are of sufficient accuracy to make this a valuable research tool in studying and characterizing the dry etch behavior of novel polymer resist materials. In situ etch rate can be measured and analyzed quickly without any prior knowledge of the polymer s physical properties. 

Zincite is usually colored red or orange by manganese impurities. Photographs of zincite are shown in Fig. 1.2. Zinc oxide crystals exhibit several typical surface orientations. The most important surfaces are the (0001) and (0001) (basal plane), (1010) and (1120) (prism planes) and (1121) (pyramidal plane) crystal faces. In principle, the (0001) planes are terminated by Zn atoms only, while the (0001) surfaces are terminated by oxygen atoms only. However, this simple picture does not hold in reality (see description of the surface structure in Sect. 4.2.1 of this book). Nevertheless, the etching behavior is noticeably different for these two surfaces [17] (see also Chap. 8). 

A simple process was used by Hickernell to determine polarity [3,95] the criterion is the etching behavior of the ZnO layer since the (OOl)-surface (O-terminated) shows an etching rate a factor of ten times greater than that of the (OOl)-surface (Zn-terminated). Perpendicular to the c-axis, the etching rate is 40-50 times the etching rate of the (OOl)-surfaces. 

Fig. 8.18. Modified Thornton-model for RF sputtered ZnO Al films according to Kluth et al. [96] Structural properties and etching behavior as function of deposition pressure and substrate temperature Ts. The SEM micrographs show cross-sections and the surface in the as-deposited state (left) and after etching in hydrochloric acid (right). The matrix of substrate temperature and deposition pressure contains structure zones according to the Thornton model [120,121]. Reprinted with permission from [96]...

Fig. 8.19. Transition of etching behavior for reactively sputtered ZnO Al films prepared at different deposition pressure 7Pa (a), 4Pa (b), and 0.6Pa (c) [122]...

While the microscopic etch mechanism of ZnO single crystals in alkaline and acid solutions is well understood [109,117], a detailed understanding of the etching behavior of compact polycrystalline films is still not available. In the following we will discuss the relation between etching behavior of... 

As a general caveat, note that an interpretation of etch results in terms of surface termination is difficult, as the microscopic structure of ZnO single crystal or ZnO Al film surfaces is unknown. Effects like surface reconstruction or presence of adsorbates may constitute the main factor determining the etching behavior, thus masking all other effects [135], A direct microscopic... 

A. Klein, Termination related features of ZnO etching behavior, private communication, 2005... 

The above cited factors influencing the hole injection kinetics have important consequences on the dark open-circuit etching behavior of GaP single crystals in alkaline Fe(CN) solutions. At the (lll)-face, the open-circuit etching rate is always found to be controlled by the rate of the charge transfer reaction (so-called kinetic control). At the (lll)-face, on the other hand, the etching rate is always found to be limited by ion diffusion towards the semiconductor surface, either of Fe(CN) (for Fe(CN) concentrations lower than 0.3 mol -1 or of OH (for Fe(CN) concentrations higher than 0.3 mol 1 ). This difference between the two polar... 

H. Fukidome, T. Ohno, and M. Matsumura, Analysis of silicon surface in connection with its unique electrochemical and etching behavior, J. Electrochem. Soc. 144, 679, 1997. 

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