High Temperature Raman Spectroscopy of Graphene
As always prepared on Silicon wafer substrates, graphene is among those materials whose properties are quite difficult to determine. Thermal properties are our focus. And we apply a home made High Temperature Raman Spectroscopy for such investigation. With the CVD-graphene sample heated in a vacuum chamber, the shift in Raman mode of graphene (G-mode) is observed, as indicated in the graph on the left.
The upper graph corresponds to the very first heating process for the sample and the tendency is obviously nonlinear. For the second heating process, which is displayed in the lower graph, the tendency changes into linear. We believe such change in tendency indicates the relaxation of the stress induced by transferring process of the sample.
Furthermore, the slope of the relaxed tendency is close to that given by a previous experiment on free standing graphene. This implies that either there was something wrong in the experiment on free standing graphene or the interaction between the substrate and the graphene is rather small.
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The upper graph corresponds to the very first heating process for the sample and the tendency is obviously nonlinear. For the second heating process, which is displayed in the lower graph, the tendency changes into linear. We believe such change in tendency indicates the relaxation of the stress induced by transferring process of the sample.
Furthermore, the slope of the relaxed tendency is close to that given by a previous experiment on free standing graphene. This implies that either there was something wrong in the experiment on free standing graphene or the interaction between the substrate and the graphene is rather small.
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Virtual Lock-in Amplifier
The technique of Lock-in amplifier greatly improves the Signal-to-noise Ratio (SNR) and thus is broadly applied. Since many calculations in a real commercialized Lock-in Amplifier can also be done by computer, we programed a virtual Lock-in Amplifier with LabVIEW. The picture on the left is a virtual panel of the amplifier.
Actually it can improve the SNR 100 times better if proper lock-in frequency is set. Moreover, a large box of circuit boards is not necessary. All you need is a computer and a serial port for input and output.
Actually it can improve the SNR 100 times better if proper lock-in frequency is set. Moreover, a large box of circuit boards is not necessary. All you need is a computer and a serial port for input and output.
LED Digital Information Transmitter
In this program, we developed a tutorial device for signal transmission. SCM(single chip microcomputer)Arduino was used for modualation and demodulation, and LED, combined with silicon photocell, for transmission. Designed as discrete parts, the device can be directly observed by users and the parameters of different parts can be reset.
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