RESUMO
Thin film multilayer materials are very important for a variety of key technologies such as hard drive storage. However, their multilayered nature means it can be difficult to examine them after production and determining properties of individual layers is harder still. Here, methods of preparing multilayer samples for examination using scanning thermal microscopy are compared, showing that both a combination of mechanical and ion beam polishing, and ion beam milling to form a crater produce suitable surfaces for scanning thermal microscopy examination. However, the larger exposed surfaces of the ion beam milled crater are the most promising for distinguishing between the layers and comparison of their thermal transport properties.
RESUMO
Using Scanning Tunnelling Microscopy (STM), the transformation from the commonly known carbon-rich (6â3×6â3)R30° reconstructed surface to graphene on the 6H-SiC(0001) substrate is systematically investigated with the aid of adsorbing cobalt (Co) which acts as a tracer to map the evolution of these surfaces. The formation of graphene is observed to begin from the step-edges as Si desorption occurs and the growth process continues akin to that of a step flow growth mode. Analysis of the surface step-height evolution at various stages of graphitization shows that as the initial (6â3×6â3)R30° surface converts to form graphene, three Si-C bilayers beneath collapse to regenerate a C-rich structure which also has a (6â3×6â3)R30° periodicity at the interface between graphene and the SiC bulk. Based on these observations, a structural mechanism for the growth of mono- and multilayer graphene is proposed. In addition, we also examine the rate at which the initial (6â3×6â3)R30° surface coverts to graphene as a function of time and temperature. Kinetic analysis of the growth process reveals that the transformation occurs with an activation energy of 3.0 ± 0.4 eV, a value close to the breaking of a Si-C bond.
