Investigations of the interactions of the germanium(100) surface with ammonia, nitric oxide, and silane

The study of semiconductors has been of longstanding interest in science and engineering. Historically, researchers have wavered between silicon and germanium as the preferred semiconductor for practical applications. Today, modern devices are predominantly constructed of Si because it has several desirable properties including thermal stability and ease of coating with a dielectric layer. But as solid state devices continue to get smaller, SiO 2 layers fail to adequately insulate and do not prevent diffusion of dopants. Problems also exist with GeO2 because it is water-soluble and, therefore, a poor choice for device fabrication. A potential replacement coating is silicon nitride. Numerous investigations of SixN y are now being made and because Ge and Si are similar in nature, a study of germanium nitride is a logical expansion of the work. For this project, the formation of GexNy through electron irradiation in a low thermal budget process was examined. Nitridation was accomplished using NH3 and NO on a Ge(100) surface at 110 K. Surface sensitive techniques used to characterize interactions include TPD, AES, XPS, LEED, ESD TOF, and HREELS. Low energy (600 eV) electrons were employed to induce or enhance the nitridation of the Ge(100) surface once it was exposed to nitrogen bearing species. It was found that NH3 did not dissociate upon adsorption to the surface but that a nitride layer was formed upon electron irradiation. Exposure to NO yielded different results, probably because NO is a highly reactive molecule and because the Ge(100) surface is also highly reactive. Spontaneous dissociation of NO on the surface occurred for high doses, and incident electrons enhanced the formation of GexN y The formation of N2 on the surface was also discovered and attributed to a possible dimerization of NO into N2O2 at low temperature. The production of N2 was verified using TOF. Experiments in which Si2H6 was exposed to the Ge(100) surface were also performed. In particular, HREELS spectra were obtained and analyzed to describe H on the surface. The data indicated that H would migrate from the adsorbed Si to the Ge if the Si2H6 dose was high enough, if the sample was annealed, or if the sample was irradiated with electrons. Finally, formation of islands by Si was verified using AFM