Growth Of Nanocrystalline Diamond Films Research Articles

Coupling Effects of CH4/H2/Ar Gas Ratios and Hot Filament-Substrate Distance on the Growth of Nanocrystalline Diamond

Due to the special shape of cutting or grinding tools used nowadays, hot filament (HF)-substrate distance is usually unavoidable during the process of diamond deposition by hot filament chemical vapor deposition (HFCVD), which will lead to difficult deposition process for nanocrystalline diamond (NCD). Based on this problem, the coupling effects of different CH4/H2/Ar gas ratios and HF-substrate distances on the growth of NCD films are systematically studied. SEM and Raman are used to analyze the surface morphology and sp3/sp2 contents of the diamond films deposited on different areas of each specimen. The results indicate that the proper increase of HF-substrate distance and concentration of CH4 or Ar encourage the growth of NCD. Under the condition of lower concentration of CH4 or Ar, NCD with uniform grain size can also be realized at a certain range of HF-substrate distance. A graph that shows the growth conditions of MCD, MCD/NCD and NCD is creatively presented by summarizing the deposition parameters and experimental results. This work provides a path to coat NCD onto the special-shaped cutting or grinding tools by HFCVD.

Investigation of a distributed antenna array microwave system for the three-dimensional low-temperature growth of nanocrystalline diamond films

In this paper the aptitude of a distributed antenna array (DAA) microwave system composed of planar matrix sources for the NanoCrystalline Diamond (NCD) film conformal coating of complex-shape 3D substrates is investigated using H2/CH4/CO2 gas mixture at low pressure and low temperature (<500 °C). First, NCD films are synthesized on 2- and 4-in. silicon wafers aligned perpendicularly (vertical samples) with respect to the plan of plasma sources. A strong heterogeneity of the layer thickness and microstructure along the vertical direction is observed but can be improved by decreasing the working pressure down to 0.25 mbar. At this pressure, NCD films synthesized on 4-in. silicon wafer at a substrate holder temperature of 400 °C show a homogeneous thickness with deviation below 15% on 3 cm along the vertical direction, which highlights the ability of the DAA reactor to treat three-dimensional substrates of a few centimeters size. A first concretization is then presented by coating a cylindrical-shape titanium implant of 6.3 mm height for biomedical applications with NCD films characterized by satisfactory purity and uniformity.

Investigation on the influence of high deposition pressure on the mcirostructure and hydrogen impurity incorporated in nanocrystalline diamond films

The impact of high deposition pressure on the microstructure and incorporation hydrogen impurity within nanocrystalline diamond (NCD) films have been investigated in a home-made microwave plasma chemical vapor deposition (MPCVD) apparatus when the microwave power and the substrate temperature were kept constant at 800 W and 650 °C, respectively. It is found that high deposition pressure not only influences the grain size and quality, but has conception link with the form and content of the bonded-H incorporated in NCD films. With the deposition pressure increases from 10 kPa to 30 kPa, the average grain size decreases from 33 nm to 13 nm and a large amount of hydrogen is detected in the obtained NCD films by Fourier transform infrared spectroscopy (FTIR). Particularly, the NCD films deposited at 15 kPa possesses the largest amount of the bonded H impurity. The optical emission spectroscopy (OES) from the plasma indicates that the intensity ratio between Hα and C2 decreases with the increase of the deposition pressure, which suggests the decline energy levels for the excited H atoms. Based on these experimental results the role of high deposition pressure on the growth of NCD films is discussed.

Nanocrystalline diamond films growth by microwave ECR CVD: Studies of structural and photoconduction properties

We report studies on growth of nanocrystalline diamond films by electron cyclotron resonance chemical vapour deposition (ECR CVD) and their structural and photoconduction properties. Bias enhanced nucleation (BEN) under higher methane partial pressure has been used to grow diamond nanocrystals with sp2 carbon clusters at grain boundaries in an amorphous carbon matrix. Structural studies indicate the size of diamond nanocrystals decreased and sp2 content increased in the films with increase in methane partial pressure, which is explained using subplantation model. Current- Voltage (I-V) measurements under dark and deep ultraviolet (DUV) light illumination conditions showed higher photocurrent in films with smaller sized diamond nanocrystals (3 nm–8 nm) compared to films having diamond nanocrystals of larger size (∼15 nm). The results indicates that the photocurrent generated in the films has major contributions from photoexcited electrons in diamond nanocrystals and sp2 carbon nanoclusters, with minor contribution from amorphous carbon phase.

Pinhole-free ultra-thin nanocrystalline diamond film growth via electrostatic self-assembly seeding with increased salt concentration of nanodiamond colloids

We demonstrate the successful chemical vapor deposition of pinhole-free extremely thin (10–50nm) nanocrystalline diamond (NCD) films to examine the potential of electrostatic self-assembly seeding with increased salt concentration of nanodiamond colloids as a nucleation enhancement step. The deposited films are characterized by scanning electron microscopy (SEM) and Raman spectroscopy to evaluate their surface morphologies and crystalline qualities. To carefully detect pinholes which are invisible via SEM, linear sweep voltammetry and cyclic voltammetry are also performed on the NCD film surfaces using the electrochemical oxidation of underlying silicon substrates. These investigations reveal that ~30nm thick continuous NCD films are successfully obtained and completely pinhole-free ~50nm thick films are reliably accessible via the proposed seeding technique.

Appropriate salt concentration of nanodiamond colloids for electrostatic self-assembly seeding of monosized individual diamond nanoparticles on silicon dioxide surfaces.

Monosized (∼4 nm) diamond nanoparticles arranged on substrate surfaces are exciting candidates for single-photon sources and nucleation sites for ultrathin nanocrystalline diamond film growth. The most commonly used technique to obtain substrate-supported diamond nanoparticles is electrostatic self-assembly seeding using nanodiamond colloidal suspensions. Currently, monodisperse nanodiamond colloids, which have a narrow distribution of particle sizes centering on the core particle size (∼4 nm), are available for the seeding technique on different substrate materials such as Si, SiO2, Cu, and AlN. However, the self-assembled nanoparticles tend to form small (typically a few tens of nanometers or even larger) aggregates on all of those substrate materials. In this study, this major weakness of self-assembled diamond nanoparticles was solved by modifying the salt concentration of nanodiamond colloidal suspensions. Several salt concentrations of colloidal suspensions were prepared using potassium chloride as an inserted electrolyte and were examined with respect to seeding on SiO2 surfaces. The colloidal suspensions and the seeded surfaces were characterized by dynamic light scattering and atomic force microscopy, respectively. Also, the interaction energies between diamond nanoparticles in each of the examined colloidal suspensions were compared on the basis of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. From these investigations, it became clear that the appropriate salt concentration suppresses the formation of small aggregates during the seeding process owing to the modified electrostatic repulsive interaction between nanoparticles. Finally, monosized (<10 nm) individual diamond nanoparticles arranged on SiO2 surfaces have been successfully obtained.

High rate growth of nanocrystalline diamond films using high microwave power and pure nitrogen/methane/hydrogen plasma

In this work, we investigate the impact of minute amounts of pure nitrogen addition into conventional methane/hydrogen mixtures on the growth characteristics of nanocrystalline diamond (NCD) films by microwave plasma assisted chemical vapour deposition (MPCVD), under high power conditions. The NCD films were produced from a gas mixture of 4% CH4/H2 with two different concentrations of N2 additive and microwave power ranging from 3.0 kW to 4.0 kW, while keeping all the other operating parameters constant. The morphology, grain size, microstructure and texture of the resulting NCD films were characterized by using scanning electron microscope (SEM), micro-Raman spectroscopy and X-ray diffraction (XRD) techniques. N2 addition was found to be the main parameter responsible for the formation and for the key change in the growth characteristics of NCD films under the employed conditions. Growth rates ranging from 5.4 μm/h up to 9.6 μm/h were achieved for the NCD films, much higher than those usually reported in the literature. The enhancing factor of nitrogen addition on NCD growth rate was obtained by comparing with the growth rate of large-grained microcrystalline diamond films grown without nitrogen and discussed by comparing with that of single crystal diamond through theoretical work in the literature. This achievement on NCD growth rate makes the technology interesting for industrial applications where fast coating of large substrates is highly desirable.

Effects of Surface Modification of Nanodiamond Particles for Nucleation Enhancement during Its Film Growth by Microwave Plasma Jet Chemical Vapour Deposition Technique

The seedings of the substrate with a suspension of nanodiamond particles (NDPs) were widely used as nucleation seeds to enhance the growth of nanostructured diamond films. The formation of agglomerates in the suspension of NDPs, however, may have adverse impact on the initial growth period. Therefore, this paper was aimed at the surface modification of the NDPs to enhance the diamond nucleation for the growth of nanocrystalline diamond films which could be used in photovoltaic applications. Hydrogen plasma, thermal, and surfactant treatment techniques were employed to improve the dispersion characteristics of detonation nanodiamond particles in aqueous media. The seeding of silicon substrate was then carried out with an optimized spin-coating method. The results of both Fourier transform infrared spectroscopy and dynamic light scattering measurements demonstrated that plasma treated diamond nanoparticles possessed polar surface functional groups and attained high dispersion in methanol. The nanocrystalline diamond films deposited by microwave plasma jet chemical vapour deposition exhibited extremely fine grain and high smooth surfaces (~6.4 nm rms) on the whole film. These results indeed open up a prospect of nanocrystalline diamond films in solar cell applications.

나노결정질 다이아몬드 seeding 효율 향상을 위한 silicon 표면 texturing

나노결정질 다이아몬드 박막 증착을 위한 전처리 공정으로 <TEX>$SF_6/O_2$</TEX> 유도결합 플라즈마를 이용하여 Si 기판 표면을 texturing하였다. <TEX>$SF_6/O_2$</TEX> 플라즈마 texturing은 2~16 범위의 매우 넓은 정규화된 표면 조도 선택성을 제공할 수 있음을 확인하였다. Texturing된 Si 기판 표면의 나노 다이아몬드 입자 seeding 이후 기존 기계적 연마 전처리에 비해 현저히 향상된 <TEX>${\sim}6.5{\times}10^{10}cm^{-2}$</TEX>의 높은 핵형성 밀도를 확보하였다. <TEX>$SF_6/O_2$</TEX> inductively coupled plasmas were employed to texture Si surface as a pretreatment for nanocrystalline diamond film growth. It was found that the <TEX>$SF_6/O_2$</TEX> plasma texturing provided a very wide process window where normalized roughness values in the range of 2~16 could be obtained. Significantly improved nucleation densities of <TEX>${\sim}6.5{\times}10^{10}cm^{-2}$</TEX> compared to conventional mechanical abrasion were achieved after seeding for the textured Si substrate.

마이크로웨이브 플라즈마 CVD에 의한 나노결정질 다이아몬드 박막 성장 시 DC 바이어스 효과

The effect of DC bias on the growth of nanocrystalline diamond films on silicon substrate by microwave plasma chemical vapor deposition has been studied varying the substrate temperature (400, 500, 600, and ), deposition time (0.5, 1, and 2h), and bias voltage (-50, -100, -150, and -200 V) at the microwave power of 1.2 kW, working pressure of 110 torr, and gas ratio of Ar/1%. In the case of low negative bias voltages (-50 and -100 V), the diamond particles were observed to grow to thin film slower than the case without bias. Applying the moderate DC bias is believed to induce the bombardment of energetic carbon and argon ions on the substrate to result in etching the surfaces of growing diamond particles or film. In the case of higher negative voltages (-150 and -200 V), the growth rate of diamond film increased with the increasing DC bias. Applying the higher DC bias increased the number of nucleation sites, and, subsequently, enhanced the film growth rate. Under the -150 V bias, the height (h) of diamond films exhibited an $h

Sputtered Tungsten-Based Ternary and Quaternary Layers for Nanocrystalline Diamond Deposition

Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.

The Nucleation and Growth of Nanocrystalline Diamond Films in Millimeter-Wave CVD Reactor

The article was devoted to the research of nanocrystalline diamond (NCD) films deposition in a novel microwave plasma-assisted CVD reactor. In this work, the seeding of silicon substrate by the spin-coating method was optimized. Hydrosol suspensions of diamond nanopowder of two types, namely, with particles having the average size of 50nm (sizes ranging from 20 to 100 nm) and 5nm (mono-dispersed powder), were used. NCD films several hundred nanometers thick were grown on prepared substrates of one and three inches in diameter. The high-density plasma in the novel reactor was generated by the gyrotron radiation at the frequency of 30 GHz. Characteristics of grown diamond films were studied by SEM, AFM and Raman spectroscopy.

Pulsed plasmas study of linear antennas microwave CVD system for nanocrystalline diamond film growth

Abstract

Aerosol deposition of detonation nanodiamonds used as nucleation centers for the growth of nanocrystalline diamond films and isolated particles

The aerosol deposition of detonation nanodiamonds (DNDs) on a silicon substrate is comprehensively studied, and the possibility of subsequent growth of nanocrystalline diamond films and isolated particles on substrates coated with DNDs is demonstrated. It is shown that a change in the deposition time and the weight concentration of DNDs in a suspension in the range 0.001–1% results in a change in the shape of DND agglomerates and their number per unit substrate surface area Ns from 108 to 1011 cm−2. Submicron isolated diamond particles are grown on a substrate coated with DND agglomerates at Ns ≈ 108 cm−2 using microwave plasma-enhanced chemical vapor deposition. At Ns ≈ 1010 cm−2, thin (∼100 nm) nanodiamond films with a root-mean-square surface roughness less than 15 nm are grown.

A new regime for high rate growth of nanocrystalline diamond films using high power and CH 4/H 2/N 2/O 2 plasma

In this work, we report high growth rate of nanocrystalline diamond (NCD) films on silicon wafers of 2 inches in diameter using a new growth regime, which employs high power and CH 4/H 2/N 2/O 2 plasma using a 5 kW MPCVD system. This is distinct from the commonly used hydrogen-poor Ar/CH 4 chemistries for NCD growth. Upon rising microwave power from 2000 W to 3200 W, the growth rate of the NCD films increases from 0.3 to 3.4 μm/h, namely one order of magnitude enhancement on the growth rate was achieved at high microwave power. The morphology, grain size, microstructure, orientation or texture, and crystalline quality of the NCD samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, and micro-Raman spectroscopy. The combined effect of nitrogen addition, microwave power, and temperature on NCD growth is discussed from the point view of gas phase chemistry and surface reactions.

Graphitized filament plasma enhanced CVD deposition of nanocrystalline diamond

A novel approach to the deposition of polycrystalline diamond is presented. The technique is based on the hot filament chemical vapour deposition technique (HFCVD). While it is similar to a high plasma power “bias enhanced growth” HFCVD, it relies on a graphite filament rather than on a metal one. It was found that with an appropriate choice of the growth parameters, 4–9% CH 4 in H 2, filament temperature > 2200 °C, 25 mBar gas pressure, plasma power > 500 W, a long filament lifetime can be achieved, when a simultaneous deposition of graphitic carbon on the hot graphite filament and of nanocrystalline diamond on a substrate facing the filament assembly is realized. In this paper the growth of nanocrystalline diamond films and their characterization (SEM, XRD, AFM) are presented. While the technique is promising for low cost, large area deposition of nanocrystalline diamond films, also the growth of microcrystalline diamond has been observed.

Role of polymers in CVD growth of nanocrystalline diamond films on foreign substrates

AbstractSpin coating of PVA polymer with fine grained diamond powder is used as the nucleation treatment for achieving growth of nanocrystalline diamond (NCD) thin films. The growth is realized by standard microwave plasma chemical vapor deposition (CVD). The morphology and character of deposited NCD film is strongly related to the growth temperature. The low temperature process (430°C) results in a growth of well‐faceted continuous films. The high temperature process (830 °C) results in voids and openings in the layer. Addition of PVA as the interlayer between the substrate and the seeding polymer composite leads to more openings. The effect is the most pronounced at 830 °C. This is assigned to thermal instability of PVA and oxygen chemistry present in the early beginning of the CVD growth. An optimized seeding process based on the polymer composite procedure at low substrate temperature and low PVA amount allows the diamond growth on extremely soft substrates.

Seeding of polymer substrates for nanocrystalline diamond film growth

Nanocrystalline diamond (NCD) thin films and structures are grown by microwave plasma CVD technique on SiO 2/Si substrates patterned by polymer. The substrates are seeded by ultra-dispersed diamond (UDD) nanoparticles in polymer, by spin coating of UDD drop and by ultrasonic treatment in solution of UDD. For all samples, the deposited NCD film is strongly related to the primary polymer deposited over the Si/SiO 2 substrate. For a certain concentration of UDD, seeding by polymer composite results in formation of fully closed layer. The drop of UDD requires using of spin coating process and by repeating of this procedure, a NCD layer with clear 3D geometry is achieved. Ultrasonic treatment leads in “implanting” of UDD into the polymer bulk. The primary polymer stripes are damaged during this procedure. In addition, 3D porous like layer is observed after the CVD growth. Optimizing the seeding procedure and the dimension of the primary polymer allow a direct growth of self-standing air bridges suitable for MEMS/NEMS applications.

Nanocrystalline Diamond Films Deposited by the Hot Cathode Direct Current Plasma Chemical Vapor Deposition Method with Different Compositions of CH4/Ar/H2 Gas Mixture

Nanocrystalline diamond films with different grain sizes were synthesized on Si substrate by the hot cathode direct current plasma chemical vapor deposition method with different compositions of CH4/Ar/H2 gas mixture. The morphology and microstructure of the obtained products were characterized by scanning electron microscopy, atomic force microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The results showed that the composition of the CH4/Ar/H2 gas mixture affected greatly the grain sizes, surface smoothness, and crystal quality of the nanocrystalline diamond films. With the increase of CH4 concentration, the grain sizes got smaller and the surface of the films got smoother. However, the grain sizes got smaller and the crystal quality was weakened with the increase of Ar concentration. In the process of deposition, SiC was formed at the substrate before the growth of nanocrystalline diamond films, which increased the secondary nucleation of nanocrystalline diamonds. To obtain the nanocrystalline diamond films with uniform small grain sizes, good surface smoothness, and little non-diamond phase, the optimal composition of the CH4/Ar/H2 gas mixture is 6/70/30 and 7/70/30.

The effect of oxygen and nitrogen additives on the growth of nanocrystalline diamondfilms

Nanocrystalline diamond (NCD) films have been synthesized byusing either nitrogen addition or oxygen addition to conventionalCH4/H2 mixtures besides themost commonly used Ar/CH4 with or without H2 chemistry. However, the synthesis of NCD films using both nitrogen and oxygen addition simultaneouslyinto CH4/H2 gases has not been reported thus far. In this work, we investigate the effect of simultaneousO2 andN2 additionto CH4/H2 plasmaon the growth of nanocrystalline diamond (NCD) films, focusing particularly on the ratio between the amountof O2 andN2 additives intoconventional CH4/H2 gas mixtures on the morphology, microstructure, texture, and crystalline quality of theNCD films. The NCD samples were produced by using a high microwave power (3 kW) in amicrowave plasma-assisted chemical vapour deposition reactor with a maximum power of 5 kWon large silicon wafers, 2 inches in diameter, and characterized by high-resolution scanningelectron microscopy, x-ray diffraction and micro-Raman spectroscopy. Our work demonstratesthat, under the conditions investigated here, NCD films can be formed when the ratio ofO2/N2 addition is increasedfrom 0 through 1 up to 7/3 (at higher than 7/3, for example 4, a large-grained polycrystalline diamond film will form), and the crystallinequality is significantly enhanced with the increase of oxygen addition. The mechanism ofO2 and N2 additives on the formation of NCD films is briefly studied.