Diamond Nano Research Articles

Optimization of electrostatic seeding technique for wafer-scale diamond fabrication on β-Ga2O3

Integrating diamonds with β-Ga2O3 is a promising solution for addressing the problem of poor thermal conductivity and limited p-type dopability of β-Ga2O3. However, growing diamonds on β-Ga2O3 is challenging, especially without any interfacial layer, and achieving large-scale uniform diamond films is also tricky. This paper explores the vital role of an electrostatic seeding technique involving the use of Polydiallyldimethylammonium chloride (PDDAC) polymer with a positive zeta potential and diamond nano slurries with a negative zeta potential to facilitate the integration of diamond with β-Ga2O3. We conduct a detailed analysis of each step of this seeding technique, adjusting the spinning speed of the polymer coating, spinning period, baking period, and ultrasonication period to understand the underlying mechanisms preventing large-scale diamond growth and to identify strategies for achieving wafer-scale diamond fabrication on single crystal β-Ga2O3 film. This process facilitates the attainment of a uniform dispersion of diamond nanoparticles on β-Ga2O3 at a seeding density of ∼1.82 × 1011 cm−2. The optimized seeding technique has enabled the successful growth of wafer-scale diamond films on β-Ga2O3, as confirmed by scanning electron microscopy (SEM). Additionally, the high quality of the diamond film is affirmed by a quality factor of 96.75 % and a narrow full-width half maximum of 10.28 cm−1 in the T2g peak of the Raman spectra. The X-ray diffraction pattern reinforces the excellent quality of polycrystalline diamond films with minimum stress. In summary, this research provides valuable insights into the polymer-assisted electrostatic seeding technique, paving the way for the uniform growth of wafer-scale diamond films on β-Ga2O3, which is critical for realizing β-Ga2O3-based heterostructure devices.

Compact and Fully Integrated LED Quantum Sensor Based on NV Centers in Diamond

Quantum magnetometry based on optically detected magnetic resonance (ODMR) of nitrogen vacancy centers in diamond nano or microcrystals is a promising technology for sensitive, integrated magnetic-field sensors. Currently, this technology is still cost-intensive and mainly found in research. Here we propose one of the smallest fully integrated quantum sensors to date based on nitrogen vacancy (NV) centers in diamond microcrystals. It is an extremely cost-effective device that integrates a pump light source, photodiode, microwave antenna, filtering and fluorescence detection. Thus, the sensor offers an all-electric interface without the need to adjust or connect optical components. A sensitivity of 28.32nT/Hz and a theoretical shot noise limited sensitivity of 2.87 nT/Hz is reached. Since only generally available parts were used, the sensor can be easily produced in a small series. The form factor of (6.9 × 3.9 × 15.9) mm3 combined with the integration level is the smallest fully integrated NV-based sensor proposed so far. With a power consumption of around 0.1W, this sensor becomes interesting for a wide range of stationary and handheld systems. This development paves the way for the wide usage of quantum magnetometers in non-laboratory environments and technical applications.

Cost-Effective Synthesis of Diamond Nano-/Microstructures from Amorphous and Graphitic Carbon Materials: Implications for Nanoelectronics

Cost-Effective Synthesis of Diamond Nano-/Microstructures from Amorphous and Graphitic Carbon Materials: Implications for Nanoelectronics

Study of The Effect Stuart and Prandtl Numbers on Diamond Nano Fluid Flowing Through Cylindrical Surface

Study of The Effect Stuart and Prandtl Numbers on Diamond Nano Fluid Flowing Through Cylindrical Surface

Plasma Enhanced Chemical Vapor Deposition of Organic Polymers

Chemical Vapor Deposition (CVD) with its plasma-enhanced variation (PECVD) is a mighty instrument in the toolbox of surface refinement to cover it with a layer with very even thickness. Remarkable the lateral and vertical conformity which is second to none. Originating from the evaporation of elements, this was soon applied to deposit compound layers by simultaneous evaporation of two or three elemental sources and today, CVD is rather applied for vaporous reactants, whereas the evaporation of solid sources has almost completely shifted to epitaxial processes with even lower deposition rates but growth which is adapted to the crystalline substrate. CVD means first breaking of chemical bonds which is followed by an atomic reorientation. As result, a new compound has been generated. Breaking of bonds requires energy, i.e., heat. Therefore, it was a giant step forward to use plasmas for this rate-limiting step. In most cases, the maximum temperature could be significantly reduced, and eventually, also organic compounds moved into the preparative focus. Even molecules with saturated bonds (CH4) were subjected to plasmas—and the result was diamond! In this article, some of these strategies are portrayed. One issue is the variety of reaction paths which can happen in a low-pressure plasma. It can act as a source for deposition and etching which turn out to be two sides of the same medal. Therefore, the view is directed to the reasons for this behavior. The advantages and disadvantages of three of the widest-spread types, namely microwave-driven plasmas and the two types of radio frequency-driven plasmas denoted Capacitively-Coupled Plasmas (CCPs) and Inductively-Coupled Plasmas (ICPs) are described. The view is also directed towards the surface analytics of the deposited layers—a very delicate issue because carbon is the most prominent atom to form multiple bonds and branched polymers which causes multifold reaction paths in almost all cases. Purification of a mixture of volatile compounds is not at all an easy task, but it is impossible for solids. Therefore, the characterization of the film properties is often more orientated towards typical surface properties, e.g., hydrophobicity, or dielectric strength instead of chemical parameters, e.g., certain spectra which characterize the purity (infrared or Raman). Besides diamond and Carbon Nano Tubes, CNTs, one of the polymers which exhibit an almost threadlike character is poly-pxylylene, commercially denoted parylene, which has turned out a film with outstanding properties when compared to other synthetics. Therefore, CVD deposition of parylene is making inroads in several technical fields. Even applications demanding tight requirements on coating quality, like gate dielectrics for semiconductor industry and semi-permeable layers for drug eluting implants in medical science, are coming within its purview. Plasma-enhancement of chemical vapor deposition has opened the window for coatings with remarkable surface qualities. In the case of diamond and CNTs, their purity can be proven by spectroscopic methods. In all the other cases, quantitative measurements of other parameters of bulk or surface parameters, resp., are more appropriate to describe and to evaluate the quality of the coatings.

Indirect overgrowth as a synthesis route for superior diamond nano sensors

The negatively charged nitrogen-vacancy (hbox {NV}^{-}) center shows excellent spin properties and sensing capabilities on the nanoscale even at room temperature. Shallow implanted hbox {NV}^{-} centers can effectively be protected from surface noise by chemical vapor deposition (CVD) diamond overgrowth, i.e. burying them homogeneously deeper in the crystal. However, the origin of the substantial losses in hbox {NV}^{-} centers after overgrowth remains an open question. Here, we use shallow hbox {NV}^{-} centers to exclude surface etching and identify the passivation reaction of NV to NVH centers during the growth as the most likely reason. Indirect overgrowth featuring low energy (2.5–5 keV) nitrogen ion implantation and CVD diamond growth before the essential annealing step reduces this passivation phenomenon significantly. Furthermore, we find higher nitrogen doses to slow down the NV–NVH conversion kinetics, which gives insight into the sub-surface diffusion of hydrogen in diamond during growth. Finally, nano sensors fabricated by indirect overgrowth combine tremendously enhanced T_2 and T_2^* times with an outstanding degree of depth-confinement which is not possible by implanting with higher energies alone. Our results improve the understanding of CVD diamond overgrowth and pave the way towards reliable and advanced engineering of shallow hbox {NV}^{-} centers for future quantum sensing devices.

Raman scattering in diamond nano- and microcrystals, synthesized at high temperatures and high pressures

The dependences of the Raman spectra of microdiamonds synthesized at high temperatures and high pressures on sizes in the range of 0.1–73.0 μm have been established. For samples several tens of microns in size, additional peaks of Raman scattering (1400 and 2619 cm−1) were found, which are interpreted as a manifestation of bound two-phonon states. A strong coupling between optical phonons in microdiamonds is predicted due to the resonator effect resulting from the confinement of phonons in diamond microcrystals.

Broadband efficient focusing on-chip integrated nano-lens

As a basic optical element, optical lens is widely used for realizing the focusing, imaging and optical communication systems. Light of different wavelengths will propagate at different speeds. A beam of polychromatic light will produce chromatic dispersion after passing through a single optical device, which prevents the ordinary lenses from focusing the light of different wavelengths into a point. This means that the light of different wavelengths cannot be focused ideally. Traditional focusing systems can solve this problem by superimposing multiple lenses, but this is at the expense of increasing the complexity, weight, and cost of the system, and is not suitable for highly integrated nano-optical systems. At present, a better solution is to use the plane metalens, that is, using the metasurface to control the amplitude, phase and polarization at each point in space. However, the plane metalens is difficult to directly integrate on the chip. An intelligent algorithm developed by combining finite element method with genetic algorithm is used to optimize the design of multi-channel on-chip wavelength router devices and polarization router devices. In this paper, combining with years’ research results of the theory of multiple scattering coherent superposition of disordered media, the use of intelligent algorithm to design an on-chip integrated nano-lens that can achieve efficient focusing from the visible to the near infrared band. In the lens structure SiO<sub>2</sub> serves as a substrate, and the arrangement structure of SiC rectangular column is designed. The substrate size is only 2 μm × 2 μm. The lens achieves low-dispersion focusing in the band from 470 nm to 1734 nm, with a focusing efficiency of over 55% at the highest level and 30% at the lowest level, and an average focusing efficiency of 42.1%. A 200-nm waveguide is added behind the focusing region. After refocusing through the waveguide, the laser beam with a size of 2 μm can be focused by the coupling of the lens and the waveguide into a beam below 200 nm in size. The focusing efficiency goes up to 80%. At the same time, the intelligent algorithm can be applied to different types of structures. The focusing lens structures composed of triangle, diamond, or circular nano columns are designed, which can achieve an approximate focusing effect and efficient coupling propagation efficiency. This work provides important ideas for developing broadband and efficient focusing nano-lens, as well as a new way to achieve the high-density integrated nanophotonic devices.

High-Pressure, High-Temperature Synthesis of Nanodiamond from Adamantane

We have studied the high-pressure, high-temperature behavior of adamantane (C10H16) and the associated formation of diamond nano- and microcrystals. Diamond microcrystals have been synthesized at a pressure of 8 GPa and temperatures above 1300–1400°C, whereas large-scale synthesis of nanodiamond has been carried out at higher pressures, near 9.4 GPa, in the narrow temperature range 1250–1330°C. Our experimental data suggest that diamond microcrystals are formed in a fluid growth medium as a result of recrystallization of graphite, an intermediate carbonization product, and that nanodiamond formation is a direct result of adamantane carbonization.

Lubrication performance of synthetic oil mixed with diamond nanoparticles: Effect of concentration

The purpose of the study is to evaluate the effect of nanoparticles concentration on the friction and wear performance of the PAO base oil. The diamond nanoparticles used in the study are mixed in varying concentrations from 0-0.8 wt. %. The experiments have been performed for a constant sliding velocity of 0.58 m/sec and a constant load of 100 N. The effect of concentration on the friction wear performance has been evaluated. Frictional characteristics are obtained on a pin on disc tribometer for steel/steel contacts. Scanning Electron Microscopy (SEM) has been carried out to study the wear behaviour of the lubricants. The results obtained from the study revealed that PAO oil containing 0.2 wt % diamond nano particles exhibited the minimum coefficient of friction (COF). The SEM images of the worn surfaces revealed that the surface damage with 0.2 wt. % is less and the wear is mainly ascribed to the ploughing effect caused by the diamond nanoparticles.

Investigation of evaporation of sessile droplets using luminescent nano-probes and other applications of NV centers in diamond

The paper describes application of diamond nano crystals to research on dynamic processes in small (less than 1 mm across) evaporating droplets deposited on a solid substrate. Such droplets are used as a model system for testing proposed bio applications of nitrogen-vacancy centers in diamond. We demonstrate that a high spatial resolution of our methods reveals unexpected features of the evaporation and fluid mechanics in such droplets.

Quantum nanophotonics in diamond [Invited

The past two decades have seen great advances in developing color centers in diamond for sensing, quantum information processing, and tests of quantum foundations. Increasingly, the success of these applications as well as fundamental investigations of light–matter interaction depend on improved control of optical interactions with color centers—from better fluorescence collection to efficient and precise coupling with confined single optical modes. Wide ranging research efforts have been undertaken to address these demands through advanced nanofabrication of diamond. This review will cover recent advances in diamond nano- and microphotonic structures for efficient light collection, color center to nanocavity coupling, hybrid integration of diamond devices with other material systems, and the wide range of fabrication methods that have enabled these complex photonic diamond systems.

Site selective growth of heteroepitaxial diamond nanoislands containing single SiV centers

We demonstrate the controlled preparation of heteroepitaxial diamond nano- and microstructures on silicon wafer based iridium films as hosts for single color centers. Our approach uses electron beam lithography followed by reactive ion etching to pattern the carbon layer formed by bias enhanced nucleation on the iridium surface. In the subsequent chemical vapor deposition process, the patterned areas evolve into regular arrays of (001) oriented diamond nano-islands with diameters of <500 nm and a height of ≈60 nm. In the islands, we identify single SiV color centers with narrow zero phonon lines down to 1 nm at room temperature.

Wafer-scale directed self-assembly of nanostructures using self-assembled monolayer based controlled-wetting

Controlled spatial placement of nanostructure (NS) at micro/nano scale has attracted much attention since the last decade due to their applications in NS based device fabrication. Different processes like, chemical interaction based to solvent driven patterned assembly of NS have been reported. This work is about the large scale patterned assembly of different NS; cobalt and diamond nano particles and ZnO nanorods at micro/nano scale by controlling the surface wetting properties. Wettable and non-wettable patterned regions were created on gold/silicon surface using patterns of self-assembled monolayer (SAM). Patterns of SAMs with terminal end of CH3 were used to create non-wettable regions on wettable gold/silicon surfaces. Micro-contact printing, e-beam lithography, and simple scratch techniques were used to create SAM patterns of different shapes and sizes. Dipping the SAM patterned surface in the NS solution or by putting a droplet of the NS solution on the patterned surface the NS assembled according to SAM patterns only in the wettable, Au/silicon regions. I observed that wettability behavior of the surface plays a dominant role in the NS assembly in comparison to van der Waals’ and other interactions between surface and the NS.

Single-step route to hierarchical flower-like carbon nanotube clusters decorated with ultrananocrystalline diamond

Two distinct forms of carbon, ultra nanocrystalline diamond (UNCD) and carbon nanotubes (CNTs), were synthesized in a single-step process via hot filament chemical vapor deposition for the first time. The synthesized structure displays unique hierarchical flower-like clusters of vertically aligned carbon nanotubes with diameters ranging from 30 to 50nm conformally coated with UNCD having a grain size in the range of 3–5nm. The seeding employed a mixture of diamond and nickel nano powders dispersed in a polymer melt, which promoted the self-assembly of sp2 and sp3 carbon into hierarchical structures. The UNCD decorated tubes show good field emission properties with low turn-on field, large field enhancement factor, and an excellent current stability over a period of over 400h. The ability to synthesize flower like structures of CNTs decorated with UNCD by a single-step process opens up new possibilities for the fabrication of robust nanoelectronic devices.

Nano-Crystalline Diamond Development and Application

diamonds have superior performance unmatched by other materials. The nano-crystalline diamond (nano-crystalline diamond powder and nano-crystalline diamond films) is a new construction material and functional material with diamond excellent properties and nano material characteristics. Such dual bizarre characteristics determine its wide application. The application developed predicts its sound prospects, which, however, requires researchers to conduct studies and development.

Influence of Additive on Diamond Films Synthesized Using Liquid Phase Electrochemical Method

An attempt was made to deposit nano-crystalline (or amorphous) diamond films on silicon and 316L stainless steel substrates by electrochemical deposition using a high-voltage pulsed generator. Alcoholic organic compounds with various concentrations of deionized water were used as electrolysis solutions. The surface morphology and crystal structure of the films were examined by scanning electron microscopy and Raman spectroscopy. Adding de-ionized water into the reaction solution can enhance the deposition rate of amorphous diamond films. The crystalline structure analysis has confirmed unambiguously the formation of diamond nano- or submicron-crystals in the deposits. It is believed that the ion H of electrochemical production plays quite similar roles to those that take place in chemical vapor deposition methods of diamond growth.

Electro-Optical Properties of Carbon Nanotubes Obtained by High Density Plasma Chemical Vapor Deposition

In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. Three methods were used for the surface modification of the sample: reference substrate (silicon wafer only submitted to a chemical cleaning), silicon wafer with surface roughness generated by plasma etching, silicon wafer with a thin iron film and silicon wafer with diamond nano powder used as precursor materials. For each kind of silicon wafer surface, the carbon nanotubes were deposited with two different deposition times (two and three hours). The carbon nanotubes structural characteristics were analyzed by Atomic Force Microscope and Scanning Electronic Microscope. The carbon nanotubes electrical characteristics were observed by Raman Spectroscopy and the carbon nanotubes electro-optical properties were analyzed by current vs voltage electrical measurements and photo-luminescence spectroscopy measurements. The photoelectric effect in the carbon nanotubes were determined by photo-induced current measurements. In this work, we obtained carbon nanotubes with semiconductor properties and carbon nanotubes with metallic properties. The electro-optical effects depend strongly on the substrate preparation and the deposition parameters of the carbon nanotubes. The carbon nanotubes are high aligned and show singular properties that can be used for many applications.

Boron-doped diamond nano microelectrodes for biosensing and in vitro measurements

Since the fabrication of the first diamond electrode in the mid 1980s, repid progress has been made on the development and application of this new type of electrode material. Boron-doped diamond (BDD) electrodes exhibit outstanding properties compared to oxygen-containing sp2 carbon electrodes. These properties make BDD electrodes an ideal choice for use in complex samples. In recent years, BDD microelectrodes have been applied to in vitro measurements of biological molecules in tissues and cells. This review will summarize recent progress in the development and applications of BDD electrodes in bio-sensing and in vitro measurements of biomolecules. In the first section, the methods for BDD diamond film deposition and BDD microelectrodes preparation are described. This is followed by a description and discussion of several approaches for characterization of the BDD electrode surface structure, morphology, and electrochemical activity. Further, application of BDD microelectrodes for use in the in vitro analysis of norepinephrine (NE), serotonin (5-HT), nitric oxide (NO), histamine, and adenosine from tissues are summarized and finally some of the remaining challenges are discussed.

Growth and characterization of diamond micro and nano crystals obtained using different methane concentration in argon-rich gas mixture

Diamond with different grain sizes and nanographite films were grown on silicon and diamond substrate using 90 vol.% argon in hydrogen and methane gas mixtures by hot filament chemical vapor deposition method (HFCVD). In current study, the methane volume concentration was varied from 0.125 to 2 vol. % in order to estimate its effect on film morphology. The substrate temperature was varied from 550 to 850 °C by external heating independently of other CVD parameters, in order to estimate the activation energy. Characterization techniques have involved Raman spectroscopy, high resolution X-ray difractometry and scanning electron microscopy. The CHEMKIN computer package has also been used to simulate the experiments. The results obtained here indicate a single mechanism for diamond growth but with a high competition with sp 2 phase's growth.