CVD grown Diamond films Research Papers (original) (raw)

Chemical vapour deposition (CVD) is used to grow diamond and diamond like carbon (DLC) films. The condition under which the formation of sp3 carbon takes place is a metastable one. There is a requirement of seed material to start the formation of diamond phase, and moreover there are substrates which favour its growth. There is still much scope of research in understanding the metastable synthesis of diamond. Such coatings need to be physically characterised and mechanically polished down to very smooth top surface for any meaningful industrial application. The work plan of the present thesis can be divided into six categories:
1. The nucleation and growth of CVD diamond is first investigated using conventional diamond micron-grit suspension seeding of silicon substrates.
2. Secondly, emphasis was given on the detonation nanodiamond (DND) seeding technique for understanding the metastable growth process of the sp3 phase. It was found that CVD growth conditions lead to capillary rise in pressure inside the vacuum chamber, which thereby replicates high pressure high temperature (HPHT) environment, thus contradicts the prevailing knowledge of metastable diamond synthesis of CVD diamond.
3. Such CVD as-grown diamond films were then characterised using different tools, like XRD, Raman, SEM, XPS etc.
4. Since, 915 MHz microwave frequency was used to grow CVD diamond, it led to coating non-uniformity, over large areas. So, such large area diamond deposition characteristics were then necessary to study.
5. Next, polishing was done on such large area diamond coatings with evaluation of its efficacy.
6. Separately, diamond like nanocomposite (DLN) coating was also deposited by a separate PECVD reactor and characterised for knee implant bio-coating application.
In the first chapter of the thesis introductory remarks have been made on the issues involving each of the above six subjects. Second chapter describes the experimental techniques adapted in the thesis work. The third chapter discusses the results obtained from these experiments to address each of the above six sub-categories. The final and fourth chapter concludes the thesis work highlighting the important observations of this PhD study.

- by Awadesh Mallik
- •
- Diamonds, Diamond Like Carbon, Nucleation and Growth, CVD grown Diamond films

Silicon carbide (SiC) is a wide band gap material that is slowly but steadily asserting itself as a reliable alternative
to silicon (Si) for high temperature electronics applications, in particular for the electrical vehicles industry.
The passivation of SiC devices with diamond films is expected to decrease leakage currents and avoid
premature breakdown of the devices, leading to more efficient devices. However, for an efficient passivation the
interface between both materials needs to be virtually void free and high quality diamond films are required
from the first stages of growth. In order to evaluate the impact of the deposition and seeding parameters in the
properties of the deposits, diamond films were deposited on SiC substrates by hot filament chemical vapor
deposition (HFCVD). Before the seeding step the substrates were exposed to diamond growth conditions (pretreatment
PT) and seeding was performed with a solution of detonation nanodiamond (DND) particles and with
6–12 and 40–60 μm grit. Diamond films were then grown at different temperatures and with different methane
concentrations and the deposits were observed in a scanning electron microscope (SEM); their quality was
assessed with Raman spectroscopy.

- by Awadesh Mallik and +1
- •
- Silicon Carbide, CVD grown Diamond films, Single Crystal

Botswana stands as a good example of a country which has beaten the “resource curse”. Resource curse is a theory which states that higher amount of natural resource creates higher risk for civil unrest and slow economic development. In contrast to the popular belief that resource rich countries economic and political upheavals, Botswana managed to fully utilize her diamond wealth. This essay will show how diamonds contributed to the development of Botswana by looking at the positive influence diamonds had on the economic, social and political dynamics of the country. This essay argues that diamonds contributed positively to the stability of Botswana as the country never experienced civil unrest, like other resource rich African countries. Because of how effectively she used her diamond wealth, Botswana was named the ‘epitome of African democracy.’ However, Botswana has been criticized for not distributing diamond wealth equally as seen by how she treats marginalized communities like the San people.

- by Kadek Hemawan
- •
- CVD grown Diamond films

We describe two example pilot efforts to help define new thermoluminescent dosimeter media.The first concerns ZnS:Mn nanophosphors prepared by chemical precipitation using zinc and sodiumsulfate, doped with manganese sulphate at concentrations varying from 1 to 3mol. The second concerns chemical vapour deposited diamond, produced as a thin film or as amorphous carbon on a single-crystal silicon substrate, eachd eposited under the same conditions, use being made of the hot filament-chemical vapour deposition (HFCVD)technique. The gas concentrations used were 1% CH4 in 99% H2 and 25%CH4 in
75% H2. Characterization of formations used FESEM, XRD and EDX. The nanophosphors consisted of
particles of sizes in the range 85–150nm, thethermoluminescence(TL)- based radiation detection
medium giving rise to a single peaked glow curve of maximum yield at a temperature of 250 oC at a
heating rate of 5 oC/s. The TL response increased linearly with radiation dose, ZnS doped to 2 mol of Mn
being found the most sensitive. Regarding chemical vapour deposited(CVD )carbon, inappreciable TL was
found for the resultant ball-like amorphous carbon films, graphite, and the silicon substrate,whereas
CVD diamond films showedapromisingdegreeoflinearitywithdose.ForboththeZnSanddiamond
samples, TLsignalfadingwasappreciable,beingsome40%perdayforZnSand450% perdayforCVD
films evenunderstorageinthedarkatroomtemperature,makingitapparentthatthereisneedtoadjust
parameterssuchasthesizeofnanoparticles.

- by Roslan Md Nor
- •
- TLD-100, CVD grown Diamond films, ZnS Nanoparticles
- by Awadesh Mallik
- •
- Nucleation and Growth, CVD grown Diamond films

Generally growth surfaces of polycrystalline microwave plasma enhanced chemical vapor deposited (MPCVD) diamond are very rough in nature. So, it is necessary to planarize the surface in order to use them in different industrial applications. High quality polycrystalline diamond (PCD) has been grown by MPCVD process and afterwards the as grown surfaces of these diamonds were polished by mechanical and/or chemo mechanical techniques. The samples were characterized for roughness by non-contact profilometer, quality by Raman spectral analysis and surface morphology by SEM images. It is concluded that mechanical polishing alone can reduce the roughness if correct combination of abrasives are selected.

- by Awadesh Mallik and +1
- •
- CVD grown Diamond films, Polishing

Nucleation and growth processes of thin diamond films on fused silica optical fibres have been investigated. Fibres were coated with diamond film using microwave plasma enhanced chemical vapour deposition (mPE CVD) system. Since the growth of diamond on the fused silica glass requires high seeding density, two types of glass pre-treatment were applied: titanium dioxide (TiO2) interlayer deposition and sonication in nanodiamond suspension. In the experiment, high density, thin (20 nm) TiO2 films were deposited using high-power impulse magnetron sputtering. Subsequently, a set of thin diamond films deposited in up to 60 min-long process was investigated. Results obtained for the two pre-treatment methods were compared. The nucleation processes were studied and compared using numerical analysis of scanning electron microscopy (SEM) images. The molecular structure of nucleated diamond was examined with micro-Raman spectroscopy. The sp3/sp2 ratio was calculated using Raman spectra deconvolution method.
Thickness, roughness and optical properties of the nanodiamond films in VIS–NIR wavelength range were investigated by means of spectroscopic ellipsometry. It was found that the high density TiO2 interlayer enhances CVD diamond film nucleation processes on fused silica and increases sp3/sp2 ratio of the film. The proposed growth method can be effectively applied in manufacturing of various types of optical fibre sensors. Due to high chemical and mechanical resistance of the diamond films such optical sensors are highly desired.

This paper focuses on reporting systematic studies on the effect of the precursor gas chemistry ratio between hydrogen/methane (H 2 /CH 4) and argon (Ar) to tailor control of the grain size, morphology and roughness of large area diamond films. Films ranging from a microcrystalline diamond structure (MCD 1–3 μm grain size) all the way to an ultrananocrystalline diamond (UNCD 3–7 nm grain size) structure were grown over 100 mm diameter areas, as a pathway for scaling diamond film growth processes by Hot Filament Chemical Vapor Deposition (HFCVD) to large areas (≥150 mm in diameter). H 2-rich/CH 4 chemistry was used to synthesize the MCD films, while Ar-rich/CH 4 /H 2 chemistry was used to grow the UNCD films. The synthesis of the diamond films using the HFCVD process indicates that the Ar content is critical to achieve the characteristic UNCD film structure with roughness , chemical bonding and thickness uniformity in the range of 5% across large areas. The ratio of Ar/H 2 in the range 70/30 sccm to 90/10 sccm, all with 2 sccm of CH 4 gas, yields films with grain size from 10–50 nm for nanocrystalline diamond (NCD) films to 3–7 nm for the UNCD films, respectively. The extremely smooth UNCD films (~3–5 nm rms) are achieved using Ar (90 sccm)/H 2 (10 sccm)/CH 4 (2 sccm) gas flows.

- by E.M.A. Fuentes-Fernandez and +3
- •
- Diamonds, UNCD, Diamond, CVD grown Diamond films

Polycrystalline diamond films of 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition at different process parameters, and their thermal conductivity is evaluated by a laser flash technique in the temperature range of 230 – 380 K. The phase purity and
quality of the films are assessed by micro-Raman spectroscopy based on diamond Raman peak width and amorphous carbon presence in the spectra. Decreasing and increasing dependencies for thermal conductivity with temperature are found for high and low quality samples, respectively. The thermal conductivity as high as 1950 ± 230 W/m·K at room temperature is measured for the most perfect material. A linear correlation between the thermal conductivity at room temperature and the fraction of diamond component the Raman spectrum for the films is established.

- by Awadesh Mallik and +2
- •
- Cell Culture, CVD grown Diamond films
- by Awadesh Mallik
- •
- Tribology, Alumina, CVD grown Diamond films

—In this paper we present a numerical analysis of Schottky Barrier Diodes (SBDs) based on CVD (Chemical Vapour Deposition) Diamond. Material and interface models suitable for TCAD (Technology Computer Aided Design) finite element simulations were implemented in the software and their validity was assessed against experimental results obtained on MIP + (Metal-Intrinsic layer-highly P doped substrate) SBDs with Al and Au as Schottky metal contacts both at room and higher temperature conditions. The paper also highlights the need to improve such TCAD models since the complex behavior of Diamond based devices is still not well captured in static and dynamic conditions. The present work also discusses the role of the Oxygen surface interface in the on state performances of the SBDs.

- by nazareno donato and +1
- •
- Numerical Simulations, Power Electronics, Diamond Model, Schottky Barrier Diode

This paper describes the science underlying the synthesis and characterization of microcrystalline diamond (MCD) to ultrananocrystalline diamond (UNCD) films on hafnium oxide (HfO 2) thin films, grown on flat Si sub-strates and micro-pillars on Si substrates, for the first time. HfO 2 is used as a novel inter-phase layer for the integration of microcrystalline (1–3 μm grain size), nanocrystalline (10–200 nm grain size), and ultrananocrystalline diamond (3–5 nm grain size) as coatings on substrates used in transformational technologies such as silicon, oxides , and metals that need protective corrosion/mechanical abrasion resistant coatings developed in this work. Atomic layer deposition was used to grow HfO 2 films with 5, 10, 30 and 100 nm in thickness, while hot filament chemical vapor deposition was used to grow diamond films, respectively. High resolution transmission electron microscopy, X-ray photoelectron and Raman spectroscopies revealed the formation of an atomic scale hafnium carbide (HfC) interphase layer on the surface of the HfO 2 film, which provides efficient nucleation for diamond film growth to produce tailored diamond surfaces on flat Si substrates and Si micro-pillars on flat Si substrates, for new transformational micro/nano-electronics and other high-tech technologies.

- by Jesus J Alcantar-Peña
- •
- Semiconductor Devices, Diamonds, Dielectrics, Diamond

In this paper, the growth of polycrystalline
chemical vapour deposition (CVD) diamond thin films on
fused silica optical fibres has been investigated. The
research results show that the effective substrate seeding
process can lower defect nucleation, and it simultaneously
increases surface encapsulation. However, the growth
process on glass requires high seeding density. The effects
of suspension type and ultrasonic power were the specific
objects of investigation. In order to increase the diamond
density, glass substrates were seeded using a high-power
sonication process. The highest applied power of sonotrode
reached 72 W during the performed experiments. The two,
most common diamond seeding suspensions were used, i.e.
detonation nanodiamond dispersed in (a) dimethyl sulfoxide
and (b) deionised water. The CVD diamond nucleation
and growth processes were performed using microwave
plasma assisted chemical vapour deposition system. Next,
the seeding efficiency was determined and compared using
the numerical analysis of scanning electron microscopy
images. The molecular composition of nucleated diamond
was examined with micro-Raman spectroscopy. The sp3/
sp2 band ratio was calculated using Raman spectra
deconvolution method. Thickness, roughness, and optical
properties of the nanodiamond films in UV–vis wavelength
range were investigated by means of spectroscopic ellipsometry. It has been demonstrated that the high-power
sonication process can improve the seeding efficiency on
glass substrates. However, it can also cause significant
erosion defects at the fibre surface. We believe that the
proposed growth method can be effectively applied to
manufacture the novel optical fibre sensors. Due to high
chemical and mechanical resistance of CVD diamond
films, deposition of such films on the sensors is highly
desirable. This method enables omitting the deposition of
an additional adhesion interlayer at the glass–nanocrystalline
interface, and thus potentially increases transmittance
of the optical system.

The transient current technique (TCT) has been adapted for profiling of the
electric field distribution in intrinsic single crystal CVD diamond. It was
found that successive hole transits do not appreciably affect the electric field
distribution within the sample. Transits of holes can therefore be used to
probe the electric field distribution and also the distribution of trapped
charge. Electron transits, on the other hand, cause an accumulation of
negative charge in the sample. Illumination with blue or green light was
shown to lead to accumulation of positive charge. Low concentrations of
trapped charge can be detected in diamond using TCT, corresponding to an
ionized impurity concentration below N = 1010 cm−3.

- by Jan Isberg
- •
- Semiconductor Physics, Electronics, Semiconductors, Diamond
- by Sandip Bysakh
- •
- Materials Science, Nucleation and Growth, CVD grown Diamond films

Black diamond is obtained by a controlled nanoscale periodic texturing of CVD diamond surface, able to drastically modify the interaction with solar radiation from optical transparency up to solar absorptance values even >90%. Surface texturing, performed by the use of an ultra-short pulse laser, is demonstrated to induce an intermediate band within the diamond bandgap supporting an efficient photoelectronic conversion of sub-bandgap photons (<5.5 eV). The intermediate band introduction results in an external quantum efficiency enhanced up to 800 nm wavelengths (and up two orders of magnitude larger than the starting transparent diamond film), without affecting the film transport capabilities. The optical and photoelectronic outstanding results open the path for future application of black diamond as a photon-enhanced thermionic emission cathode for solar concentrating systems, with advantages of excellent electronic properties combined with a potentially very low work function and high thermal stability.

- by Paolo Calvani and +1
- •
- Solar Energy, Femtosecond Laser Materials Processing, CVD grown Diamond films

The optical properties of diamond spherical-like particles, prepared by the hot-filament chemical vapor deposition technique on opal substrates, have been investigated. The particles were studied using scanning electron microscopy, micro-Raman spectroscopy and micro-photoluminescence techniques. The diamond particles, consisting of polycrystalline diamond, have a size of about 5 lm. Periodic peaks in the background of the photoluminescence spectra have been revealed. Analysis of the position of these peaks with the Lorentz– Mie theory for light scattering by single dielectric spherical particles confirms that these observed peaks can be regarded as whispering-gallery mode.

- by Yury Rakovich
- •
- Raman Spectroscopy, Photoluminescence, Optical microresonators, Raman

By performing Time-of-Flight measurements on high-purity single-crystalline chemical vapor deposited diamond, we are able to extract the electron drift velocity of valley-polarized electrons in the low-injection regime. The aim of this study is to improve the understanding of the mechanisms involved in the conduction-band transport of valley-polarized electrons. The measurements were carried out within the temperature range of 10–80 K, and the experimental results are systematically compared with Monte Carlo charge transport simulations. We observe a rapid enhancement of the electron mobility with decreasing temperature, which reveals that inelastic effects in electron-phonon scattering become important below ∼40 K. In addition, we obtain the momentum relaxation rate for electrons with different valley polarizations.

- by Saman Majdi
- •
- Engineering, Quantum Physics, Chemistry, Monte Carlo Simulation
- by Sobia Sajid
- •
- Materials Engineering, Chemical Engineering, Electron Microscopy, Raman Spectroscopy
- by Sobia Sajid
- •
- Nanocrystalline Material, CVD grown Diamond films

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- by Peter Bogle
- •
- CVD grown Diamond films
- by Said Ahzi and +1
- •
- Engineering, Technology, Titanium, Crystallization

By performing Time-of-Flight measurements on high-purity single-crystalline chemical vapor deposited diamond we are able to extract the electron drift velocity of valley-polarized electrons in the low-injection regime. The aim of this study is to improve the understanding of the mechanisms involved in the conduction-band transport of valley-polarized electrons. The measurements were carried out within the temperature range 10 to 80 K and the experimental results are systematically compared with Monte Carlo charge transport simulations. We observe a rapid enhancement of the electron mobility with decreasing temperature, which reveals that inelastic effects in electron-phonon scattering become important below ~40 K. In addition, we obtain the momentum relaxation rate for electrons with different valley polarizations.

- by Jan Isberg and +1
- •
- Quantum Physics, Monte Carlo Simulation, Electronics, Semiconductors

This paper reports the effects of MeV ion irradiation on the adhesion and quality of diamond films on WC-Co tool-bits and silver films on soda glass. Diamond films of about 3 μm thickness were prepared, using the hot filament CVD technique, on WC-Co tool-bits. Silver films of 1000 Å thickness were prepared, using the Joule evaporation technique, on soda glass. 100 MeV 127I beam was irradiated on the films at various doses up to 1 × 1014 ions/cm2. Adhesion strength was measured using a pin-pull test. Scotch tape test was also performed on some of the films. SEM images show no morphological modifications of the diamond films after irradiation. Laser Raman spectra show that the irradiation causes almost complete elimination of non-diamond carbon present in the films. Adhesion strength of the diamond films as determined by Pin-pull test show improvement at least by 65 kgf/cm2 after irradiation. Improvement in the adhesion of silver films is found to be dependent on the amount of electronic energy loss (Se) at the film-substrate interface. It is shown that for silver film on soda glass is needed if the adhesion is required to be achieved at a dose of 1 × 1013 ions/cm2 using ion irradiation of 100 MeV 127I beam. Main cause of the improvements in the adhesion and quality of the films is suggested to be the energy deposited to the electronic system of the material by the projectile ion.

One dimensional C-C nanostructure, diamond-graphite nanorods, was synthesized by the argon rich microwave plasma chemical vapor deposition method. The nanostructures were characterized by scanning electron microscopy and transmission electron microscopy techniques. The diamond nanorods (DNRs) consist of single-crystalline diamond cores of 2-5 nm in diameter and several tens of nanometer in length. The DNRs are encapsulated in a graphitic shell of variable thickness. Raman and X-ray diffraction spectra also indicated the coexistence of diamond and graphite phases in the film. The addition of nitrogen is considered to be helpful for the highly efficient formation of graphite shell. The high content of methane in the gas mixture in the presence of argon rich environment is suggested to be responsible for the one dimensional growth. (C) 2009 Elsevier B.V. All rights reserved.

- by Sobia Sajid
- •
- CVD grown Diamond films

Nanocrystalline diamond (NCD) films were grown on silicon substrates by hot filament chemical vapor deposition in Ar/N-2/CH4 gas mixtures. The effects of seeding process prior to deposition, the total gas pressure, and concentration of nitrogen on the grain size, morphology and bonding nature in HFCVD technique were investigated. The results indicated that a low total gas pressure is favorable for nanosized diamond crystallites. Films micrograph obtained from scanning electron microscopy showed diamond nanograins elongated with the addition of nitrogen in the plasma. Crystal structure investigations were carried out by X-ray diffraction measurements for deposited films. An increase in the size of crystallite is also observed from XRD measurements in NCD film when nitrogen was added in plasma. From Raman spectra, it was observed that the relative intensity of G peak increases indicating more graphite content after nitrogen added in the plasma. The effects of the nitrogen incorporation in nanocrystalline films in HFCVD are discussed. (C) 2009 Elsevier B.V. All rights reserved.

- by Sobia Sajid
- •
- Nanocrystalline Material, CVD grown Diamond films