Chemistry Reference
In-Depth Information
9
Summary and Closing Remarks
9.1. COMPLEXITY
Silicon exhibits a diverse range of electrochemical phenomena, such as current oscil-
lation, anisotropic etching, formation of porous silicon, etc. Each of these phenomena
has extremely rich details that are governed by complex relationships between struc-
tures and properties of silicon electrodes on the one hand and between properties and
experimental conditions on the other. The silicon/electrolyte interface is a complex
system in which a great many variables are interacting with each other in a great many
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ways.
The physical and chemical nature of the silicon/electrolyte interface, in terms of
carrier type and density, charge distribution and transfer, surface reactions, evolution
of surface geometry, etc., are determined by numerous variables as illustrated in Fig.
9.1. Each of these variables is a continuum of a wide dimensional range and its effect
on the electrode properties involves time and micro-surface geometry. Thus, the pos-
sible conditions determined by the combinations of these variables are infinite, respon-
sible for the diverse phenomena and complex details observed on silicon electrodes.
The experimental results on silicon electrodes generated in the past decades have been
overwhelming, but many phenomena on silicon electrodes are still not fully character-
ized due to their complex nature. Also, what occurred in the past indicates that the more
is known about the system the more questions are generated. Thus, in a philosophical
sense, the details of the system may never be completely revealed because every time
a phenomenon is characterized at one temporal-spatial scale under a condition, further
details with increasing complexity start to emerge at a finer scale or under a new
condition.
The high degree of details that have already been characterized on silicon elec-
trodes is associated with the great diversity of conditions that have been explored,
the high sensitivity in experimental control and measurement, and the large number
of investigations made in the past. In particular, many details could not be experimen-
tally resolved without the high sensitivity in experimental control and measurement.
To this end the most important control has been for the silicon substrate, which is con-
veniently available in single crystalline form of high quality to researchers of all fields.
Such high degree of standardization and availability has been unique to silicon. No
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