Study of graded Ni-Ti shape memory alloy film growth on Si(100) substrate
Study of graded Ni-Ti shape memory alloy film growth on Si(100) substrate
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Si(100)基体上梯度Ni-Ti形状记忆合金薄膜生长研究
DOI：
10.1007/s00339-008-4397-2
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
F. B. Braz Fernandes
中科院分区：
文献类型：
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作者：
R. Martins;N. Schell;A. Mücklich;H. Reuther;M. Beckers;R.J.C. Silva;L. Pereira;F. B. Braz Fernandes
采用原位X射线衍射（XRD）技术研究了在沉积Ni-Ti薄膜过程中有意改变Ti/Ni比对薄膜性能的影响。因此，梯度薄膜沉积表现出独特的组成和晶体结构沿着生长方向。溅射膜的非原位俄歇电子能谱（AES），横截面透射电子显微镜（XTEM），和电阻率（ER）测量（在热循环过程中）。在本文中，结果提出有关的膜（厚度为420 nm）的中心部分（范围从50到60原子%）和近等原子组成的四肢，以下四个不同的沉积期（不同的Ti目标功率）的Ti-丰富的组合物。在初始沉积步骤（近等原子组成）期间，由于天然Si氧化物（2-3 nm）的存在，Ni-Ti B2相通过堆叠到自然氧化的Si（100）衬底上的（h 00）平面上而开始。第二、三步中Ti靶功率的增加诱导了Ti_2Ni的析出。当停止Ti共溅射时，Ti 2Ni溶解，并且因此起到Ti储库的作用，用于形成现在优先堆叠到（110）上的B2相，其中系统再次接近等原子组成。界面形态的非原位研究表明存在NiSi 2硅化物（A-NiSi 2和B-NiSi 2）、Ti4 Ni 4Si 7、Ti 2Ni和由Ni、Ti和Si构成的非识别相，最有可能是无定形的。在热循环过程中，ER测量揭示了与B2，R-相和B19′相相关的相变。这些类型的研究允许在沉积和退火过程中的中间状态的识别，以及与膜的最终结构的相关性，对于优化沉积参数以制造具有双向可逆致动的膜是有用的。
In-situ X-ray diffraction (XRD) was employed to study the effect of the deliberate change of the Ti/Ni ratio during the deposition of Ni-Ti films. Thus, graded films were deposited exhibiting distinctive composition and crystalline structure along the growth direction. The as-sputtered films were ex-situ characterized by Auger electron spectroscopy (AES), cross-sectional transmission electron microscopy (XTEM), and electrical resistivity (ER) measurements (during thermal cycling). In this paper results are presented concerning a film (thickness of ≈ 420 nm) with a Ti-rich composition in the central part (ranging from 50 to ≈60 at. %) and near-equiatomic composition in the extremities, following four distinct deposition periods (different Ti target powers). During the initial deposition step (near-equiatomic composition) the Ni-Ti B2 phase starts by stacking onto (h00) planes on the naturally oxidized Si(100) substrate due to the presence of the native Si oxide (2–3 nm). The increase of the power of the Ti target in the second and third steps induced the precipitation of Ti2Ni. When stopping the Ti co-sputtering, Ti2Ni dissolves and, thus, plays the role of a Ti reservoir for the formation of B2 phase now preferentially stacking onto (110) with the system approaching again the equiatomic composition. The ex-situ study of the morphology of the interface has shown the presence of NiSi2 silicides (A-NiSi2 and B-NiSi2), Ti4Ni4Si7, Ti2Ni and a non-identified phase constituted by Ni, Ti and Si, most likely amorphous. During thermal cycling, ER measurements revealed phase transitions associated with the B2, R-phase and B19′ phases. These type of studies allow the identification of intermediate states during deposition and annealing, and the correlation with the final structure of the film, being useful for the optimisation of the deposition parameters in order to fabricate films with a two-way reversible actuation.