Integration of graphene with Si microelectronics is very appealing by offering a potentially broad range of new functionalities. New materials to be integrated with the Si platform must conform to stringent purity standards. Here, we investigate graphene layers grown on copper foils by chemical vapor deposition and transferred to silicon wafers by wet etching and electrochemical delamination methods with respect to residual submonolayer metallic contaminations. Regardless of the transfer method and associated cleaning scheme, time-of-flight secondary ion mass spectrometry and total reflection X-ray fluorescence measurements indicate that the graphene sheets are contaminated with residual metals (copper, iron) with a concentration exceeding 10(13) atoms/cm(2). These metal impurities appear to be partially mobile upon thermal treatment, as shown by depth profiling and reduction of the minority charge carrier diffusion length in the silicon substrate. As residual metallic impurities can significantly alter electronic and electrochemical properties of graphene and can severely impede the process of integration with silicon microelectronics, these results reveal that further progress in synthesis, handling, and cleaning of graphene is required to advance electronic and optoelectronic applications.

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This paper reviews the experimental and theoretical state of the art in ballistic hot electron transistors that utilize two-dimensional base contacts made from graphene, i.e. graphene base transistors (GBTs). Early performance predictions that indicated potential for THz operation still hold true today, even with improved models that take non-idealities into account. Experimental results clearly demonstrate the basic functionality, with on/off current switching over several orders of magnitude, but further developments are required to exploit the full potential of the GBT device family. In particular, interfaces between graphene and semiconductors or dielectrics are far from perfect and thus limit experimental device integrity, reliability and performance

The decreasing feature size of integrated circuits requires new low-temperature, chlorine-free CVD processes for titanium nitride (TiN) diffusion barriers. The thermal deposition of TiN from organometallic precursors, e.g., tetrakis(dimethylamido)titanium (TMT), results in a high carbon contamination of the films. Using in situ X-ray photoelectron spectroscopy (XPS), we show that the contamination of TiN films deposited on silicon consists mostly of hydrocarbon inclusions and a smaller amount of titanium carbide (TiC). From these results we confirm and extend the mechanism for the thermolysis reaction of TMT proposed by other authors, showing the formation of TiC as being inherent to this precursor. The reaction of TMT with ammonia decreases the amount of carbon contamination, yet the spontaneous reaction in the gas phase results in a poor step coverage. On the basis of these results, we suggest in agreement with other authors that at small NH3/TMT ratios and very low pressures the reaction proceeds via a polymeric transamination at the substrate surface. The importance of gas-phase reaction increases at higher NH3/TMT ratios. Activated hydrogen from a plasma afterglow source significantly reduces the hydrocarbon contamination leaving only a small amount of hydrocarbon and carbidic carbon in the films. It is shown that at least a part of the aliphatic carbon found in the films originates from the adsorption and subsequent decomposition of the product amines at the TiN surface. Attempts to avoid the TiC formation were made by using the precursor bis[N,N‘-bis(tert-butyl)ethylenediamido]titanium (BTET).