三甲基镓在Pd(111)表面吸附解离及表面预吸附H和O的影响

利用X-射线光电子能谱（XPS）和程序升温脱附谱（TPD）研究了三甲基镓在Pd（111）表面的吸附和解离行为，并考察了表面预吸附H和O的影响。结果表明，在吸附温度为140 K时，三甲基镓在Pd（111）上主要为解离吸附，此时表面物种为Ga（CH₃）_x （x=1，2，3）和CH_x物种。加热将导致Ga的甲基化合物中的Ga-C键发生分步断裂，在不同温度下产生CH₄和H₂从表面脱附。同时，XPS结果证实了在275~325 K的温度区间内存在Ga甲基化合物的分子脱附。退火至更高温度，表面只观察到积碳和金属Ga物种，这二者随着温度的继续升高逐渐向体相扩散。在Pd（111）表面预吸附O和H对上述吸附和解离行为存在显著的影响。当表面预吸附H时，脱附产物CH₄和H₂的脱附主要位于315 K，可归属为一甲基镓的解离脱附。当表面预吸附O时，只在258 K观察到CH₄和H₂的脱附峰，可能来自于Pd-O-Ga（CH₃）₂吸附结构的解离.

Surface Chemistry of Ga(CH3)3 on Pd(111) and Effect of Pre-covered H and O

The adsorption and decomposition of trimethylgallium (Ga(CH₃)₃, TMG) on Pd(111) and the effect of pre-covered H and O were studied by temperature programmed desorption spectroscopy and X-ray photoelectron spectroscopy. TMG adsorbs dissociatively at 140 K and the surface is covered by a mixture of Ga(CH₃)_x (x=1, 2 or 3) and CHx(a) (x=1, 2 or 3) species. During the heating process, the decomposition of Ga(CH₃)₃ on clean Pd(111) follows a progressive Ga-C bond cleavage process with CH₄ and H₂ as the desorption products. The desorption of Ga-containing molecules (probably GaCH₃) is also identi ed in the temperature range of 275-325 K. At higher annealing temperature, carbon deposits and metallic Ga are left on the surface and start to di use into the bulk of the substrate. The presence of precovered H(a) and O(a) has a signi cant effect on the adsorption and decomposition behavior of TMG. When the surface is pre-covered by saturated H₂, CH₄, and H₂ desorptions are mainly observed at 315 K, which is ascribed to the dissociation of GaCH₃ intermediate. In the case of O-precovered surface, the dissociation mostly occurs at 258 K, of which a Pd-O-Ga(CH₃)₂ structure is assumed to be the precusor. The presented results may provide some insights into the mechanism of surface reaction during the lm deposition by using trimethylgallium as precursor.