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Preparation and Mechanical Properties of Metal Thin Films

Author: YinLiTao
Tutor: ZhaoDongMei；RenFengZhang
School: Henan University of Science and Technology
Course: Materials Science
Keywords: Electrodeposition process multilayers internal stress micro-hardness grain
CLC: TQ153.1
Type: Master's thesis
Year: 2009
Downloads: 106
Quote: 2
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Abstract

Ag、Ni and Cu metal films and the Cu/Ag、Ni/Ag、Cu/Ni multilayers were prepared by direct current electrodeposition. The impacts of Electrolyte composition and processing paramaters on films were studied. The internal stress of Cu films and Ni films deposited on pure iron was measured by insitu operational excurved-cathode method, and the results verified the point about the composition and origin of the internal stress of films in Cheng’s electronic theory.The cyanide-free silver electroplating process of the thiosulfates was used in this experiment. Two kinds of electroplate liquid of AgNO3 and AgBr were chosen to prepare Ag films on pure Cu substrate. When AgNO3 of the main salt in AgNO3 electroplate liquid was 40 g?L-1 and the current density was 0.25A?dm-2, the films and the substrates had a good bond and the grain size was 30nm. When AgBr of the main salt in AgBr electroplate liquid was 30 g?L-1 and the current density was 0.2A?dm-2, the films and the substrates had a good bond and the grain size was 55nm. Two kinds of electroplate liquid met the test requirements to prepare the nanocrystal Ag films, moreover, AgNO3 electroplate liquid had a wider range of current density, and performances of electroplate liquid was more stable.Ni films were obtained by the process of bright nickle plating. The effects of C12H24NaSO4, saccharin and GL-100 on fimls of micro-surface morphology, hardness, grain size and texture and the relation between current density and hardness were studied. The results show that the films’grains prefers to grow on (200) crystalplane when C12H24NaSO4 is added solely. The texture of (111)crystalplane occurs when saccharin and GL-100 are added in the electro-bath. saccharin refines the grains observably. In the same condition, the film hardness increases with the increase of current density.The bright Cu films were prepared by electroplating in the sulfate. The effect of current density on hardness and the role of the electrolyte composition and the common faults and maintenance methods were studied. The results show that the film thickness and hardness increases with the increase of current density.Cu/Ag、Ni/Ag and Cu/Ni multilayers were obtained on the basis of single films. The microstructures of three kinds of metallic multilayers with different periodic thickness were analysed by SEM, and their hardness were measured by micro-hardness instrument. SEM observation shows that the boundaries between heterogeneous layers are clear and the layer thicknesses are uniform. The film hardness appears strain softening when the periodic thickness of multilayers is closed to or achived 100nm.The measurements of the internal stress in Cu films and Ni films on pure iron verified the electronic theory proposed by Cheng, and it points out that the internal stress can be divided into the interface stress and the growth stress. The interface stress generates due to the continuity of electron density at interface.

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