Specific Process Knowledge/Thin film deposition/Deposition of Gold/Adhesion layers: Difference between revisions
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= Adhesion layer model = | = Adhesion layer model = | ||
Based on the results obtained above, a revised adhesion layer model for Ti/Au and Cr/Au thin-�lm systems is proposed. The model is intended as | |||
an improvement in the description of the layer-layer interaction compared | |||
to the model described in Section 5.1, with the aim of helping the thin-�lm | |||
engineering of nanodevices. | |||
The adhesion layer model is shown in Fig. 5.15. The growth of both | |||
adhesion layers starts with the deposition of the atoms on the substrate (1) | |||
and the subsequent formation of an amorphous layer (2). During the deposition, | |||
both Ti and Cr get partially oxidized by oxygen and water molecules | |||
present on the substrate surface and in the deposition chamber. The adhesion | |||
layer acts as a wetting layer for Au, reducing the nucleation energy | |||
barrier and increasing the number of nucleation sites compared to the case | |||
where Au is directly evaporated onto the SiO2 surface. The enhanced wetting | |||
is due to the formation of Ti-Au and Cr-Au chemical bonds. This leads | |||
to the formation of a continuous �lm having i) monodisperse grain size and | |||
ii) the energetically most favorable [111] crystal orientation for Au (3). For | |||
the Cr/Au system there is an extra step: the inter-di�usion between Cr and | |||
Au to form a Cr-Au alloy (4). Such di�usion is limited to a thickness of 2-3 | |||
nm for samples prepared at room temperature. | |||
= Recommendations for nanodevice fabrication = | = Recommendations for nanodevice fabrication = | ||