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Sunday, May 7, 2017

#369 Bulk and the surface

Considering properties of semiconductor material in the form of the wafer for instance, it would be a mistake to consider it as a perfectly homogenous piece of the solid. In reality, distinction between its bulk and its surface needs to be made. That is because physical characteristics between these two parts of semiconductor material very significantly.   


In general terms, surface is an exterior face of the solid and represents two-dimensional termination of fundamental characteristics displayed by the three-dimensionally distributed atoms in the bulk of the sample. In the case of crystals, surface also represents an abrupt discontinuity of crystal structure. In contrast to the atoms in the bulk, atoms on the open surface have by definition at least one bond unsaturated. Such unsaturated (dangling) bonds at the surface are electrically active and unless neutralized these bonds will feature electric charge commonly referred to as surface states which will cause changes in the distribution of electric charge in the sub-surface region of semiconductor. Furthermore, atoms on the surface are the only ones that are exposed to and interacting with an ambient. Such interactions affect surface characteristics and induce their instabilities.


This is just a rough illustration of the reasons for which surface and bulk properties of semiconductor are drastically different. More on this, and related topics on the other occasion.


Posted by Jerzy Ruzyllo at 02:13 PM | Semiconductors | Link is the personal blog of Jerzy Ruzyllo. With over 35 years of experience in academic research and teaching in the area of semiconductor engineering (currently holding position of a Distinguished Professor of Electrical Engineering and Professor of Materials Science and Engineering at Penn State University), he has a unique perspective on the developments in this progress driving technical domain and enjoys blogging about it.

With over 2000 terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today.

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