Growth and characterization of rare-earth monosulfides for cold cathode applications

We report the successful growth of bulk cubic lanthanum sulfide (LaS) and n eodymium sulfide (NdS). Powder x-ray diffraction scans of the samples show the rocksalt phase with a lattice constant a(0) = 5.857(2) Angstrom and 5.6 94(2) Angstrom for LaS and NdS, respectively. In Raman scattering, one obse rves the vibrational density of states (cubic symmetry) and identifies the longitudinal optical and transverse acoustic phonons at 261(284) and 100(92 ) cm(-1) with LaS(NdS), respectively. These rare-earth monosulfides offer a ttractive alternatives to the commonly used cesiated surfaces to reach nega tive electron affinity at various III-V semiconductor surfaces. (C) 2001 Am ericana Vacuum.