In order to investigate light wavelength selectivity of
graphene, its photoconductivity in respect to IR response and
temperature is analyzed.
As the graphene layer is extremely thin and transparent, a
focused laser beam is used to heat it up through the inverted
microscope. To distinguish the effect from temperature
dependence of graphene, temperature calibration of laser
heating was performed with the Keithley 6517b and its
thermocouple prior to the measurement of IR
photoconductivity. The thermocouple probe was placed onto
the fresh glass substrate on top of the inverted microscope
sample stage. Then the IR laser source was turned on to heat
up the sample while measuring simultaneously the
temperature. The recorded data in repeated laser switch on and
off was shown in Fig. 6. Because of the limited power of laser
source (120mW) and the size of the focused area (1µm)
through magnified lens objective, temperature was saturated
at around 60°C.