Direct Growth of Patterned Ge on Insulators Using Graphene

Abstract

Graphene sheets were formed on a Si substrate with a 300-nm-thick SiO2 layer. The graphene sheets partially covered the SiO2 surface. Ge was deposited on the surface by sputtering. The fabricated samples were evaluated with Raman spectroscopy and atomic force microscopy. We found that Ge was formed on the graphene surface selectively when the substrate temperature was 450 °C or higher during the deposition. The results of the Raman spectroscopy indicated that sp3 defects were introduced into the graphene sheets after the deposition. Such defects can be an important factor in the selective adsorption of Ge on graphene sheets because sp3 defects are highly reactive. A growth temperature of more than 450 °C was needed for the selective deposition, indicating that the surface diffusion of the Ge adatoms on the insulating surface during the deposition is also important. The selective deposition of Ge on the graphene sheets is considered to be due to the sp3 defects introduced into the graphene sheets and surface diffusion of the Ge adatoms on the SiO2 surface. This direct-patterning technique on insulators can be utilized for various materials that can be deposited by sputtering.

Microstructure and Ferromagnetism of Mn0.05Ge0.95 Quantum Dots/Graphene Heterostructures for Spintronic Devices

“…The G peak near 1580 cm –1 and the 2D peak near 2700 cm –1 can be observed in the bare graphene layer, whereas after the sputtering D peak near 1350 cm –1 appears and the 2D peak disappears. The D peak originates from the vibration in disordered sp 2 carbon structures and is related to the symmetry-breaking feature. , Thus, the appearance and increasing width of the D peak after the sputtering process suggest the structure change of graphene and that the defects are introduced into the graphene. , Meanwhile, the samples after deposition underwent a blue shift in G peaks and a red shift in 2D peaks compared with the bare graphene substrate, which was attributed to the tensile strain and doping effect, respectively. The tensile strain can be put down to the carbon atoms stretching when germanium atoms form the Ge–C bonds on the surface of graphene.…”

“…The D peak originates from the vibration in disordered sp 2 carbon structures and is related to the symmetry-breaking feature. 34,40 Thus, the appearance and increasing width of the D peak after the sputtering process suggest the structure change of graphene and that the defects are introduced into the graphene. 41,42 Meanwhile, the samples after deposition underwent a blue shift in G peaks and a red shift in 2D peaks compared with the bare graphene substrate, which was attributed to the tensile strain and doping effect, respectively.…”

“…Sputtering, as a common semiconductor epitaxial growth method, has been reported to apply for the self-assembled growth of graphene-based germanium QDs. 34 Compared with the molecular beam epitaxy (MBE) method, the IBSD method has realized the fabrication of highquality epitaxial thin films and low dimensional nanomaterials with low cost, convenient control, and industrial production. 35−37 Li et al successfully grew uniform and regular Mn 0.03 Ge 0.97 QDs on silicon substrates using IBSD.…”

“…In addition, the work function of graphene is lower than that of silicon, and when graphene and Mn x Ge 1– x QDs form a zero-dimensional/two-dimensional heterostructure, a higher potential barrier is generated to increase the hole concentration and enhance the hole-mediated exchange coupling in Mn x Ge 1– x QDs, thus enhancing ferromagnetism. Sputtering, as a common semiconductor epitaxial growth method, has been reported to apply for the self-assembled growth of graphene-based germanium QDs . Compared with the molecular beam epitaxy (MBE) method, the IBSD method has realized the fabrication of high-quality epitaxial thin films and low dimensional nanomaterials with low cost, convenient control, and industrial production. − Li et al successfully grew uniform and regular Mn 0.03 Ge 0.97 QDs on silicon substrates using IBSD .…”