Structure and phase behavior of the Ir(001) surface: X-ray scattering measurements

We present the results of X-ray scattering studies of the structure and pha se behavior of the Ir(001) surface between room temperature and T = 2000 K. Two distinct phases have been identified. For temperatures above T = 1950 K, the Ir(001) surface is rough, similar to what has been observed for Pt(0 01) at elevated temperatures. Below about T = 1950 K, the surface reconstru cts to farm a quasi-hexagonal unit cell, which is commensurate with the sub strate lying beneath it. The measured X-ray intensities, both inplane and a long the specular rod, are consistent with a buckled, (5 x 1) description o f the structure, including a 15% expansion of the top layer spacing and an enhanced surface Debye-Waller factor. A detailed comparison is made of the phase behavior determined here for Ir(001) to that found earlier for Pt and Au(001). (C) 1999 Elsevier Science B.V. All rights reserved.