N-Type Conductive Ultrananocrystalline Diamond Films Grown by Hot Filament CVD

We present the synthesis of ultrananocrystalline diamond (UNCD) films by application of hot filament chemical vapor deposition (HFCVD). We furthermore studied the different morphological, structural, and electrical properties. The grown films are fine grained with grain sizes between 4 and 7 nm. The UNCD films exhibit different electrical conductivities, dependent on grain boundary structure. We present different contact metallizations exhibiting ohmic contact behavior and good adhesion to the UNCD surface. The temperature dependence of the electrical conductivity is presented between −200 and 900°C. We furthermore present spectroscopic investigations of the films, supporting that the origin of the conductivity is the structure and volume of the grain boundary.

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Microstructures, Grain Boundaries and Superplasticity in Fine Grained Ceramics

MRS Proceedings ◽

10.1557/proc-196-313 ◽

1990 ◽

Vol 196 ◽

Cited By ~ 4

Author(s):

C. Carry

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Boundary Segregation ◽

Boundary Structure ◽

Fine Grained ◽

Chemical Effects ◽

Liquid Phases ◽

Grain Boundary Structure ◽

Wide Range ◽

Points Of View

ABSTRACTDeformation studies in compression and in tension have clearly shown evidence for superplasticity for a wide range of fine grained ceramics from both macroscopic and microscopic points of view. The main purpose of this paper is to focus attention on chemical effects in ceramic grain boundaries which can lead to a great variety of behavior. Grain boundary segregation or precipitation, residual impurities or doping elements, and glassy or liquid phases at grain boundaries can strongly affect the macroscopic flow properties of superplastic fine grained ceramics. Some microstructural and grain boundary features, mainly in two oxide materials (alumina and yttria doped zirconia), are analyzed, compared, and discussed in connection with their observed superplastic behavior. Special attention is devoted to the relation between the overall chemistry of the materials (impurities and doping elements) and to the grain boundary structure and chemistry (segregation, precipitation, intergranular phases). Some consequences and implications on the tailoring of ceramic microstructures for superplasticity are discussed. In addition, some recent hot forming and hot bonding experiments are also reported.

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Control of Boundary Structure and Grain Growth for Microstructural Design

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.3891 ◽

2005 ◽

Vol 475-479 ◽

pp. 3891-3896 ◽

Cited By ~ 1

Author(s):

Si Young Choi ◽

Suk Joong L. Kang

Keyword(s):

Grain Boundary ◽

Grain Growth ◽

Grain Structure ◽

Boundary Structure ◽

Basic Principles ◽

Fine Grained ◽

Grain Boundary Structure ◽

Fine Grained Structure ◽

The Difference ◽

And Control

The design of microstructure in materials, ranging from ultrafine, moderately sized, duplex to single crystalline, has long been a challenging subject to material scientists. A basic means to achieve this goal is related to the control of grain growth. Taking BaTiO3 as a model system, this investigation shows that control of grain boundary structure between rough and faceted and control of initial grain size can allow us to achieve the goal. When the grain boundary is rough, normal grain growth occurs with a moderate rate. On the other hand, for faceted boundaries, either abnormal grain growth or grain growth inhibition occurs resulting in a duplex grain structure or fine-grained structure, respectively. Growth of single crystals is also possible when the boundary is faceted. During crystal growth amorphous films can form and thicken at dry grain boundaries above the eutectic temperature. As the film thickness increases, the growth rate of the crystals is reduced. This observed growth behavior of grains with boundary structure is explained in terms of the difference in mobility between the two types of boundaries. The results demonstrate the basic principles of obtaining various microstructures from the same material.

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Two Investigations into Grain Boundary Structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100080833 ◽

1977 ◽

Vol 35 ◽

pp. 688-691

Author(s):

P. Humble

Keyword(s):

Grain Boundary ◽

Dark Field ◽

Boundary Structure ◽

Boundary Dislocation ◽

Bright Field ◽

Intrinsic Structure ◽

Weak Beam ◽

Grain Boundary Structure ◽

Independent Information ◽

Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

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Relationships Between Grain Boundary Structure and Material Properties

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001550 ◽

1980 ◽

Vol 38 ◽

pp. 366-369

Author(s):

Brian Ralph ◽

Barlow Claire ◽

Nicola Ecob

Keyword(s):

Grain Boundary ◽

Material Properties ◽

Main Property ◽

Grain Structure ◽

Boundary Structure ◽

Grain Boundary Structure ◽

Property Changes

This brief review seeks to summarize some of the main property changes which may be induced by altering the grain structure of materials. Where appropriate an interpretation is given of these changes in terms of current theories of grain boundary structure, and some examples from current studies are presented at the end of this paper.

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