Controlled Growth of Graphene on Porous Silicon

Graphene as the most thin, two-dimensional atomic crystal material, which is made of sp 2 hybrid carbon atoms, has unique properties, such as mechanical stiffness, strength and elasticity, very high electrical and thermal conductivities. These unusual properties have caused the emergence of tantalizing potential applications, ranging from field effect transistors to chemical and biochemical sensors. On the other hand, As an important porous material, more and more attention has been paid for porous silicon produced by electrochemical etching due to its wide applications In this work, we demonstrate a hybrid material combining graphene and porous silicon together and focus on the study of the properties of porous silicon based graphene materials. A series of porous silicon substrates with different pore sizes are fabricated through electrochemical etching by varying the current density. Then, graphene films are transferred to the porous silicon substrate. The effects of morphology and porosity of porous silicon on the properties of graphene have been investigated. In our experiment, highly-doped n-type samples (0.01-0.02 Ωcm, 300 μm- thick, CZ-grown, (1 0 0)-oriented and polished) were used. A set of anodizing experiments were performed at different applied current densities (50-500 mA/cm 2 ), and the anodizing solution was composed of 48% aqueous HF ,30wt.% aqueous H 2 O 2 and 99.7vol.% ethanol in a variety of concentrations. Corrosion time is set to 5 min. Next, graphene is transferred to the surface of porous silicon substrate by the transferring process. Fig. 1a shows the top-view SEM picture of the pores covered with graphene. The porous silicon was fabricated by anodization for 5 min with current density of 150 mA/cm 2 . Micro-Raman spectrometer was used to confirm the quality of graphene. Fig. 1b shows the result of Raman measurement of the porous silicon based graphene. The G and 2D peaks locate at 1588 cm -1 and 2683 cm -1 , respectively, demonstrating the graphene is well transferred to the porous silicon substrate with good quality. Figure 1