Understanding the microscopic processes by which the electrons within condu
ctors are scattered at surfaces and interfaces is important for both fundam
ental physics and technology. The authors review what has been learned sc,
far about scattering of electrons at a variety of surfaces and interfaces u
sing a technique, transverse electron focusing (TEF), that involves two poi
nt contacts in a uniform magnetic field. Transverse electron focusing is a
sort of beta-ray spectrometer in a metal, except that, whereas the beta-ray
spectrometer requires a narrow beam because the energy and momentum of a f
ree electron can be arbitrary, in TEF the electrons of interest all have th
e Fermi energy and momentum, so focusing occurs even for electrons injected
isotropically in angle. Transverse electron focusing is unique in its abil
ity to probe localized and selectable portions of the interface from inside
the conductor, using conduction electrons on only small parts of the Fermi
surface. The authors first briefly review the essential features of TEF an
d of ideal and rough surfaces and describe the three techniques now used fo
r injecting and detecting electrons: needle contacts, lithographically fabr
icated contacts. and light-induced injection. They then turn to measurement
s in metals and semimetals of the probability of specular reflection q from
a given interface for electrons at the Fermi energy impinging at perpendic
ular incidence. They examine how q varies over different crystal faces for
different electron orbits on the Fermi surfaces of a variety of conductors
and how it is affected by changes in the de Broglie wavelength lambda(dB),
by chemical etching, ion etching, or physical damage, by a molecular overla
yer condensed from the surrounding atmosphere, and, for semimetals, by surf
ace band bending (surface charge). The authors also explain how to measure
the dependence of q upon the angle of incidence q(theta), which gives infor
mation about surface structure. Transverse electron focusing studies of a v
ariety of quasiparticle effects arising because the electrons are in a soli
d are described. These include (a) scattering of excitations moving on "hol
elike" orbits-q can depend upon the sign of the particle charge; (b) scatte
ring involving a surface reciprocal-lattice vector G(r), including surface
resonances induced by an artificial grating etched onto a Bi Surface; and (
c) scattering between different parts of the Fermi surface-intervalley scat
tering (IVS)-including scattering in which the sign of the quasiparticle ch
arge changes. The authors review studies of scattering of electrons from a
normal-metal (or semimetal)/superconductor interface, which involves an unu
sual phenomenon called Andreev reflection, in which the signs of both the c
harge and mass change. Also described are TEF studies of scattering of ligh
t-excited electrons from an intercrystalline boundary and recent TEF measur
ements of q for scattering from the boundary of the two-dimensional electro
n gas. The authors conclude with a list of future TEF studies of conduction
-electron/interface interactions that they believe to be interesting and im
portant. [S0034-6861(99)01105-8].