Ct. Dervos, RELIABILITY OF THE ASPERITY CONTACT MODEL IN DETERMINING CHARGE INJECTION ACROSS INTERFACES, IEEE transactions on components, packaging, and manufacturing technology. Part A, 18(2), 1995, pp. 353-363
Current profiles across mechanically contacted materials usually diffe
r from the ones obtained by corresponding evaporated contacts. The asp
erity contact model has been brought up to cover such discrepancies. H
owever, there is a lack of experimental evidence concerning its applic
ability on electronic injection across the interfaces. The work presen
ted in this paper uses I-V curves of a well-documented device, the met
al-semiconductor contact, as a tool to examine the validity of the asp
erity contact model and the implications of the interfacial layer, the
axial contact force, the interfacial field and the relative permittiv
ity of the surrounding space, on the injection process. Namely, the in
fluence of interfacial layers has been studied in ultra-high-vacuum (U
HV) environment (10(-10) mbar) using cleaved silicon samples, contacte
d by hemispherical metal electrodes (Au, Cu, In, Al) covered insitu by
fresh overlayers. The applied axial forces were controlled by electro
magnets which displaced stainless steel electrodes to contact chemical
ly prepared and cleaved [110] Si samples in a UHV environment. The imp
ortance of the interfacial fields has been examined by using Si and Ga
As samples having specific surface profiles, i,e., mesas with 10 mu m
diameter and 1 mu m height, fabricated by plasma etching or wet chemis
try processes. Finally, the effect of the relative permittivity of the
surrounding space has been investigated by applying sinusoidal 50-Hz
high current densities on metal-metal contacts in the laboratory and h
igh vacuum (10(-6) mbar) environments. Utilizing the framework of the
theory of the asperity contact model, the obtained results are in good
agreement with the expected implications of the examined factors.