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1

X-Ray Topographic Study of a Homoepitaxial Diamond Layer on an Ultraviolet-Irradiated Precision Polished Substrate

100%

Kato Y., Umezawa H., Shikata S.

Acta Physica Polonica A

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2014

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vol. 125

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issue 4

969-971

EN

Suitable techniques for the growth of high-quality single-crystal diamond are needed in order to use single-crystal diamond in power devices. Because the ion plantation technique cannot be used for diamond doping, a drift layer and a conduction layer for a diamond power device were grown by chemical vapor deposition. An important challenge in this field is to reduce the dislocation density in the epitaxial layer. The dislocation density was found to increase during the chemical vapor deposition process. Because a defective surface is one cause of increased dislocation density, the use of a UV-polished substrate having no scratches due to mechanical polishing was investigated.

2

High Temperature Surface Conductivity of Hydrogenated Diamond Films Exposed to Humid Air

100%

Stec K., Szroeder P., Benzhour K.

Acta Physica Polonica A

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2010

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vol. 118

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issue 3

511-514

EN

Surface conductivity of thin diamond films was measured as a function of temperature up to 450°C. Hydrogenated diamond was synthesized by chemical vapor deposition in hydrogen/carbon plasma. Low values of charge carrier activation energy ( ≈ 10 meV) were observed, when hydrogenated diamond films were exposed to the ambient humid air. However, the activation energy increased by two orders of magnitude as film temperature exceeded 300°C. We have attributed this behavior to the desorption of the H_2O adlayer. The jump of the activation energy did not occur, when experiment was performed in vacuum. We have also shown that donor doping leads to the up-shift of the Fermi level much above the acceptor-like band gap levels induced by surface C-H bonds, which cannot be compensated by transfer of electrons from diamond to the double H-H_2O layer.

3

Structural and Electrical Characterization of Undoped Diamond Layer Grown by HF CVD

80%

Banaszak-Piechowska A., Paprocki K., Fabisiak K., Dudkowiak A., Szybowicz M., Staryga E.

Acta Physica Polonica A

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2017

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vol. 132

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issue 4

1411-1414

EN

The undoped diamond layers were prepared using hot filament chemical vapor deposition technique. The controlled variation of the deposition parameters resulted in the layers with varying amount of nondiamond impurities. Routine characterization of the layers was carried out using scanning electron microscopy, X-ray diffractometry, and the Raman spectroscopy. Detailed measurements of room temperature electrical conductivity (σ₃₀₀), current-voltage characteristics have yielded useful information about the electrical conduction mechanism in this interesting material. The σ₃₀₀ and I-V characteristic measurements were done in sandwiched configuration taking care off the surface effects. The diamond shows room temperature dc conductivity reaching the values in the range of σ₃₀₀ ≈0.1-1 μS/cm. The I-V characteristics in these layers show space charge limited conduction behavior with I ~ V² in high voltage region. The obtained results are explained in terms of chemically adsorbed hydrogen on the surface of diamond layers, which is a source of acceptor states just above the top of valence band.

4

Optimization of Polycrystalline CVD Diamond Seeding with the Use of sp³/sp² Raman Band Ratio

80%

Golunski L., Sobaszek M., Gardas M., Gnyba M., Bogdanowicz R., Ficek M., Plotka P.

Acta Physica Polonica A

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2015

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vol. 128

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issue 1

136-140

EN

The influence of various nanodiamond colloids used for seeding nondiamond substrates in microwave plasma enhanced chemical vapour deposition diamond process was investigated. Colloids based on deionized water, isopropanol alcohol and dimethyl sulfoxide (DMSO) were used with different grain size dispersion: 150, 400 and 35 nm, respectively. The influence of growth time was also taken into consideration and bias enhanced nucleation. Microcrystalline diamond films were deposited on the seeded substrates in microwave plasma chemical vapour deposition using hydrogen-methane gas mixture. Seeding efficiency was investigated by means of scanning electron microscopy and Raman spectroscopy. Authors defined the new factor called as diamond ideality factor (di) which can give a quick estimation of quality of film and relative sp³ content. Few main peaks were identified at the following wave numbers: diamond sp³ peak 1332 cm^{-1}, D band peak 1355 cm^{-1}, C-H bending peak 1440-1480 cm^{-1} and G band peak 1560 cm^{-1}. The best di was achieved for DMSO based colloid in all cases. The application of bias enhanced nucleation increases the diamond crystals size and the sp³/sp² ratio.

5

Study of the Thermoluminescence of CVD Diamond

80%

Karczmarska A., Mitura-Nowak M., Nowak T., Marszałek M.

Acta Physica Polonica A

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2012

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vol. 121

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issue 2

510-513

EN

This work reports some thermoluminescent properties of chemical vapour deposition diamond film grown by 5 kW microwave assisted plasma chemical vapour deposition. The 2" diamond sample with the thickness of 32 μm was exposed to gamma radiation in the dose range 0.6-55 Gy. The thermoluminescent glow curve of diamond sample displayed a peak with the maximum centered at 240°C. The linearity of the detector response in the range of 10-55 Gy was observed. The bleaching effect, seen as fading of the thermoluminescent signal when the device was exposed to light in the visible range, was also noticed. Two-dimensional dose distribution was measured using 2D thermoluminescent reader equipped with a sensitive 640 × 480 pixels charge coupled device camera. The surface morphology of the diamond film was observed with scanning electron microscope and atomic force microscope. The grain size was estimated as about 15 μm. The Raman spectroscopy was used to characterize phase purity. The width and position of the diamond Raman band around 1332 cm^{-1} indicated that the coating is crystalline and of good quality. It is concluded that good quality chemical vapour deposition diamond coating could be promising material for thermoluminescent dosimetry.

6

Processing and Mechanical Properties of B₄C/Diamond Impregnated Fe/Co MMC

70%

Öksüz K., Şimşir M.

Acta Physica Polonica A

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2015

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vol. 127

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issue 4

1139-1141

EN

Cobalt is currently used in the production of diamond reinforced metal matrix composites (i.e. stone-cutting tools). Herein, how sintering temperature and matrix composition influences the material properties of diamond reinforced MMCs was explored. The aim of this work is to produce diamond reinforced metal matrix composites based on Fe-Co compositions with and without B₄C are processed by a PM method using a hot pressing technique. The effects of Fe and B₄C additions on the characteristic of diamond impregnated Co matrix composites have been investigated. Samples reinforced with and without B₄C having two different compositions (different Fe/Co ratio) were produced under 25 MPa pressure and sintered at 1000°C temperature. After sintering, hardness tests were carried out and wear tests were performed by pin-on-disc. The results showed that addition of Fe caused slightly decrease in the hardness of the matrix. However, reinforcing with B₄C increased the hardness of the matrix. It is observed that wear resistance of B₄C reinforced Fe-Co metal matrix composite was greater than that of composites without reinforcement. SEM and EDX techniques were used to characterize the composites.

7

Nanocrystalline CVD Diamond Coatings on Fused Silica Optical Fibres: Optical Properties Study

70%

Ficek M., Bogdanowicz R., Ryl J.

Acta Physica Polonica A

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2015

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vol. 127

|

issue 3

868-873

EN

Seeding and growth processes of thin diamond films on fused silica optical fibres have been investigated. Glass pre-treatment by dip coating in two detonation nanodiamond (DND) seeding media has been studied. The DND suspension in ethyl alcohol and dispersion of DND in dimethyl sulfoxide (DMSO) with polyvinyl alcohol (PVA) were chosen for the seeding purpose. The grain size distribution of nanodiamond particles in both seeding media was kept at the same level (approximately 10-50 nm). After the seeding nanocrystalline diamond films were deposited on the fibres using microwave plasma assisted chemical vapour deposition system. The results of the process were investigated using numerical analysis of scanning electron microscopy images. The molecular structure of diamond has been examined with micro-Raman spectroscopy. Thickness, roughness and optical properties of the nanocrystalline diamond films in VIS-NIR wavelength range were investigated on reference samples using spectroscopic ellipsometry. Light reflection at the fibre end-face for different deposition parameters was also investigated. Proposed seeding method can be further effectively applied for manufacturing of optical fibre sensors. Due to extraordinary properties of diamond, which include high chemical and mechanical resistance, such films are highly desired for optical sensing purposes.

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X-Ray Topographic Study of a Homoepitaxial Diamond Layer on an Ultraviolet-Irradiated Precision Polished Substrate

High Temperature Surface Conductivity of Hydrogenated Diamond Films Exposed to Humid Air

Structural and Electrical Characterization of Undoped Diamond Layer Grown by HF CVD

Optimization of Polycrystalline CVD Diamond Seeding with the Use of sp³/sp² Raman Band Ratio

Study of the Thermoluminescence of CVD Diamond

Processing and Mechanical Properties of B₄C/Diamond Impregnated Fe/Co MMC

Nanocrystalline CVD Diamond Coatings on Fused Silica Optical Fibres: Optical Properties Study