Molecular depth profiling with cluster ion beams
Molecular depth profiling with cluster ion beams
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DOI：
10.1021/jp0573341
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发表时间：
2006-04-27
影响因子：
3.3
通讯作者：
Winograd, N
中科院分区：
文献类型：
--
作者：
Cheng, J;Wucher, A;Winograd, N
用C-60（+）和Au-x（+）高能簇离子束轰击（x = 1,2,3）表征了多肽掺杂海藻糖薄膜。这些研究的目的是通过测量腐蚀过程中的二次离子质谱来获得肽和海藻糖分子溅射过程的信息。该系统非常重要，因为可以在Si衬底上重复制备类似300nm厚度的均匀薄膜，从而可以详细表征不同射体的深度分布。用一个简单的解析模型描述了分子离子强度随离子剂量的函数的基本形式。该模型包括诸如分子溅射率、海藻糖或肽的损伤截面以及抛射改变的表面层厚度等参数。结果表明，当溅射总产率高、改变层厚度小时，获得了成功的分子深度剖面的有利条件。尽管C-60的化学损伤累积程度略低，但所有簇射弹都获得了成功的分子深度剖面。在C-60轰击下，约20nm的层厚改变和约5nm的损伤截面在物理上与类似化学体系的分子动力学计算预测一致。总的来说，所提出的模型应该为优化实验参数提供指导，以最大限度地提高复杂分子薄膜衬底的分子深度剖面实验的信息量。
Peptide-doped trehalose thin films have been characterized by bombardment with energetic cluster ion beams of C-60(+) and Au-x(+) (x = 1, 2, 3). The aim of these studies is to acquire information about the molecular sputtering process of the peptide and trehalose by measurement of secondary ion mass spectra during erosion. This system is important since uniform thin films of similar to 300 nm thickness can be reproducibly prepared on a Si Substrate, allowing detailed characterization of the resulting depth profile with different projectiles. The basic form of the molecular ion intensity as a function of ion dose is described by a simple analytical model. The model includes parameters such as the molecular sputtering yield, the damage cross section of the trehalose or the peptide, and the thickness of a surface layer altered by the projectile. The results show that favorable conditions for successful molecular depth profiling are achieved when the total sputtering yield is high and the altered layer thickness is low. Successful molecular depth profiles are achieved with all of the cluster projectiles, although the degree of chemical damage accumulation was slightly lower with C-60. With C-60 bombardment, the altered layer thickness of about 20 nm and the damage cross section of about 5 nm(2) are physically consistent with predictions of molecular dynamics calculations available for similar chemical systems. In general, the model presented should provide guidance in optimizing experimental parameters for maximizing the information content of molecular depth profiling experiments with complex molecular thin film substrates.