The interaction of Cl 2 with Bi(0001): Incipient BiCl 3 formation and decomposition

Abstract

The interaction of Cl 2 with Bi(0001) has been studied using low-energy electron diffraction (LEED), Auger electron spectroscopy (AES), electron energy loss spectroscopy (ELS), thermal desorption spectroscopy (TDS) and work function measurements (Δφ). The initial sticking probability (∼ 0.14) is nearly temperature- and coverage-independent for 120 < T < 300 K and θ Cl < 1.1 × 10 15 atoms cm −2. The adsorbed layer decomposes as BiCl 3 gas at ∼ 370 K with an activation energy for desorption (∼ 24 kcal mole −1) near the sublimation energy of solid BiCl 3 (28 kcal mole −1). The ( 2 3 × 2 3 )R30° LEED pattern for saturation coverage at room temperature suggests a single, close-packed layer of adsorbed BiCl 3 molecules upon Bi(0001) substrate sites in a distorted form of the molecular lattice of solid BiCl 3. Below one-third of saturation (θ Cl < 5.3 × 10 14 atoms cm −2), the p(1 × 1) pattern suggests chlorine atoms adsorbed upon Bi(0001) substrate sites. These surface structural models are corroborated by AES, ELS, TDS and Δθ results. These results for the semimetal Bi are favorably compared with periodic trends extended from the transition metal series, proving that local and atomic characteristics rather than long-range electronic proporties mitigate surface reactivity and chemisorption phenomena.