Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 11, pp. 1928−1933.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
A.A. Nechitaylov, N.V. Glebova, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 11, pp. 1779−1784.
OF SYSTEMS AND PROCESSES
Differential Thermal Analysis of Porous Silicon
A. A. Nechitaylov and N. V. Glebova
Ioffe Physicotechnical Institute, St. Petersburg, Russia
Received September 21, 2009
Abstract—Porous silicon materials, macro- and mesoporous silicon, obtained by electrochemical anodic etching
of n- and p-Si were studied by differential thermal analysis at a steady temperature rise and under isothermal
conditions in nitrogen atmosphere and in air. The method was used to estimate the presence and amount of phases
of surface volatile compounds. The possibility was studied to perform a comparative estimate of the specific
surface area of different types of porous silicon from data on the surface oxidation kinetics determined by the
dynamic differential thermal analysis in air.
The use of porous silicon in fuel cell (FC) is one of
the rapidly developing applications. Macroporous silicon
is widely applied in multifunctional FC elements as
gas-leading channel, electrode, or catalyst support .
The use of mesoporous silicon as matrix for platinum
nanoparticles is interesting from the standpoint of
increase of the catalyst efﬁ ciency . To employ silicon-
like layers, it is necessary to study their properties and
evaluate the corresponding characterization methods.
In this work, the layers of macro- and mesoporous
silicon were studied by the differential thermal analysis
Samples of porous silicon were prepared by
electrochemical anodic etching of (100) oriented one
side polished plates of crystalline silicon about
We used commercial silicon plates, KEF-15, KDB-16,
and KDB-0.01 (diameter 76 mm) made of phosphorus-
doped silicon with electron conductivity (n-Si) or of
boron-doped silicon with hole conductivity (p-Si). The
plates were cut with a diamond scriber into
20 × 20–25 ×
On the n–Si plates, a heavily-doped (n
) layer of about
2 μm thickness, ensuring the uniform distribution of
electrical contact throughout the plate upon etching, was
formed on the back side, to which electrical contact was
applied. This was done by diffusion doping of phosphorus
1100°C for 2 h. As a source of phosphorus served
orthophosphoric acid. The doped plates were cooled, and
the oxide formed on the surface was dissolved in a 1:1
hydroﬂ uoric acid. After that, the plates were washed
in deionized water and centrifuged (rotation rate about
On the p–Si plates, a window with a heavily-doped
) layer in the oxide mask, ensuring the hole generation
upon etching within a limited region, was formed on the
back side, to which electrical contact was applied. This
was done by boron diffusion doping at
1100°C for 2 h.
rthoboric acid was used as boron source. The cooled
samples were withdrawn and pressed into the etching cell,
whose insert was 1-2 mm lesser in diameter than etching
region, and the window in the silicon oxide was dissolved
in a 1:1 hydroﬂ uoric acid. Then, the samples were washed
with water and withdrawn from the cell.
Then, onto an open window in the silicon oxide, one
drop of 1% boric acid ethanol solution was poured, and
the sample was dried in air. The dry samples were placed
into a quartz box and a quartz tube and doped there. After
cooling, the samples were placed into the cell again, and
the window area having been opened before the doping
was opened again (the boundaries of the window could