2. Experimental details
Si-NPA was prepared by hydrothermally etching (1 1 1) oriented
single crystal silicon (sc-Si) wafer in a solution of hydrofluoric acid
containing ferric nitrate which has been described in detail previously
[10]. The growth of the 3C–SiC nanograins on Si-NPA was
realized in a closed graphite crucible which was placed in a vacuum
furnace and heated to 1000 ◦C, just as depicted in our other letter
[16]. The only alternation in this experiment is the carbonization
time which was prolonged from 1 h to 3 h. When the sample was
taken out after carbonization, one side of it was carefully polished
by a sand paper as far as the sc-Si wafer was exposed and then
the whole sample was cleaned with acetone and then 1% HF. In
succession, two layers of aluminum (∼500 nm) were deposited on
SiC and sc-Si by a vacuum evaporation method. The integral device
was annealed at 300◦ C in Ar atmosphere for 30 min to realize good
ohmic contact between the electrodes and the semiconductors.
The surface morphology and elemental composition of ascarbonized
Si-NPA were characterized by field-emission scanning
electron microscope (FE-SEM), X-ray diffractometer (XRD) and
Raman spectroscopy. The photoluminescence (PL) spectra were
measured by SPEX (SPEX Inc., Fairfield, NJ) SPEXF212 fluorescence
spectrometer. The electrical properties were measured through an
electrical group system mainly composed of Soucemeter-2400 and
Nanovolt-Meter (Keithley Instruments, Inc., San Jose, CA).