Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Model for the Optical Absorption in Porous Silicon Quantum Wires   In this paper, we analyse the optical absorption in porous silicon . This is
the first attempt to explicitly demonstrate that it is not possible to extract
the band gap of such low dimensional nanostructures like porous silicon from a
Tauc plot of Square Root(alpha h nu) vs (h nu) . These objections are also
valid for other reduced dimensional systems like quantum wires and quantum dots
etc.
  So we model the absorption process assuming that porous silicon is a pseudo
1D material system having a distribution of band gaps. We show that in order to
explain the absorption we specifically need to invoke - (a) k is not conserved
in optical transitions,(b) the oscillator strength of these transitions depends
on the size of the nanostructure in which the absorption takes place and (c)
the distribution of band gaps significantly influences the optical absorption.
A natural explanation of the temperature dependence of absorption in porous
silicon also follows from our model . We have also shown that porosity can be
inferred non-destructively from transmission measurements in the region of low
absorption.
  One can easily generalize our equations and use them to analyse the
absorption process of other low dimensional materials too .

10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex