Surface hillocks

In addition to pit formation, it is possible for hillocks to be formed on the surface. Hillocks may be formed from humps on the pre-etched surface, protective spots on parts of die surface, or the growing together of etch pits. 

In particular, the hillocks formed on the (100) surface are crystallographic structures bounded by four (111) planes resulting from the anisotropic etching and their formation directly contributes to the roughness of the surfaces. Hillocks may, under certain conditions, form in HF-based solutions, " but most commonly in alkaline etchants. ° Because the (111) surface etches very slowly, the formation of hillocks leads to a decreased etch rate. ... 

In an ultra-high vacuum, no surface hillocks were found to grow on aluminum (Al) surfaces under compression (Ref 24). Hillocks grow on Al surfaces only when the Al surface is oxidized, and Al surface oxide is known to be protective. Without surface oxide, the free surface of Al is a good source and sink of vacancies, so a compressive stress can be relieved uniformly on the entire surface of the Al, based on the Nabarro-Herring model of lattice creep or the Coble... 

The infrared spectra demonstrate that there is a strong interaction between CR and the PS segment of SBS and between SBS and BR. Scanning electron micrographs of the fracture surfaces further support the conclusion. The fracture surface of 70 30 BR/CR shows layer-shaped morphology and 30 70 blends show hillock-shaped protmsions. Addition of 5% SBS reduces the particle size, makes the particles more spherical, and enhances uniform distribution. This provides further evidence of the compatibilizing effect of SBS. 

Zeolite/polymer mixed-matrix membranes prepared from crosslinked polymers and surface-modified zeolite particles offered both outstanding separation properties and swelling resistance for some gas and vapor separations such as purification of natural gas. Hillock and coworkers reported that crosslinked mixed-matrix membranes prepared from modified SSZ-13 zeolite and 1,3-propane diol crosslinked polyimide (6FDA-DAM-DABA) synthesized from 2,2 -feis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, p-dimethylaminobenzylamine-and 3,5-diaminobenzoic acid displayed high CO2/CH4 selectivities of up to 47 Barrer and CO2 permeabilities of up to 89 Barrer under mixed gas testing conditions [71]. Additionally, these crosslinked mixed-matrix membranes were resistant to CO2 plasticization up to 450 psia (3100kPa). 

Hillock, A.M.W., Miller, S.J., and Koros, W.J. (2008) Crosslinked mixed matrix membranes for the purification of natural gas effects of sieve surface modification./. Memhr. Sci., 314, 193-199. 

Not all the dislocations outcropped on a crystal surface are active growth centers. In Fig. 6.6, the distribution of growth hillocks on a (111) face of an as-grown Ba(N03)2 crystal is compared with the distribution of dislocations revealed by X-ray... 

Fig. 1. The accuracy of e-beam lithography is illustrated in the scanning electron micrograph (top). The size of the features formed in the silicon oxide is 0.5 pm and the typical animal cell (a fibroblast) has a diameter of 20 pm. This kind of cell adheres actively to surfaces, forming thin filopodia which here have all attached to the micro-hillocks. Semiconductor technology is capable of manufacturing micro-electrodes, sensors, pores and electronic networks with sizes smaller than that of the cell. The lower illustration summarises the main detection and measuring methods currently in use...

Etchants will attack either concave or convex irregularities on the surface, such as formed by gas bubbles during solidification or at irregular growth steps. The pits left after a dislocation has been removed usually give results similar to a concavity (sections 2.1 and 2.2). The shape of these pits or hillocks are determined by the orientation of the surface and the type of attack of the etchant (i. e., preferential or non-preferential). There is no way at present to predict what planes will be revealed by a given etchant it is not yet even possible to predict whether a given solution will act preferentially or nonpreferentially. 

An attempt was made to show that not all pits or hillocks produced on surfaces by any of the various etching processes are formed at dislocations. Some of the causes of etch pitting were discussed, and techniques for differentiating between the various pits were described. 

When etching n-GaP photoanodically in the onset region I of the photocurrent-potential curve (Table 2, cases M, N, O), etch hillocks and ridges are observed at the surface after removal of only a small amount of material (see, e.g., Fig. 20). In this region of the i- V curve, recombination of the photogenerated charge carriers... 

Formation of hillocks and penetration twins on the (100) surface of single crystal diamond was studied by Tsuno et al. [101]. The misorientation of the (100) surface was less than 3° from the exact (100) lattice plane. A NIRIM-type... 

Figure 6.8. (a) Surface structure with a growth hillock and a penetration twin, and (b) its atomic configuration [101]. 

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