A wavelength-selective silicon monolithic (+, -, - +) channel-cut monochrom
ator and a system for high-precision measurements of lattice spacing were d
eveloped at the Photon Factory BL3C2. A computer program was developed to a
llow us to measure automatically more than 30 different samples within a si
ngle run. The full-width at half-maximum of the rocking curves of a couple
of (8 0 0) GaAs reflections is 17-20 arc-sec. Using this system, it is poss
ible to carry out precise lattice spacing measurements of GaAs single cryst
als with high boron concentrations by the Bond method. The standard deviati
ons for the measurements of one sample were estimated by Deltaa/a= 4 x 10(-
8). Anomalous reductions in lattice spacing have been found below a boron c
oncentration of 1 x 10(19) cm(-3). (C) 2001 Elsevier Science B.V. All right
s reserved.