The distribution of oxidation states changes with the preparation conditions and with the quality of the interface. Synchrotron radiation is essential for achieving the surface sensitivity that is necessary to detect the 1-2 monolayers of silicon atoms in the interface region. Wide-gap semiconductors, such as diamond, silicon carbide, and gallium nitride, are gaining interest for high power, high temperature devices and for light emission in the blue. The figure shows the energy shift of the 1s level for carbon atoms at the diamond surface , which are arranged into pi-bonded chains . This technique provides the ultimate control in growing semiconductor structures.
Every atomic layer is deposited separately in a two-step process.
A self-saturating monolayer is adsorbed first and then activated for adsorption of the next layer. Our focus is on deposition of silicon and carbon, e.g. for tailoring silicon carbide structures with variable band gap. The key problem appears to be the controlled deposition of carbon , which is traditionally done at high temperature without any possibility for atomic control. We have found that compounds with carbon atoms bonded to more than one silicon have the best chance to remain at the surface during the activation process, whereas single-bonded hydrocarbon groups desorb. The discovery of conducting polymers with efficient luminescence has opened prospects for fabricating flat panel displays.