Diamond Arrays Research Articles

Development of Diamond and Silicon MEMS Sensor Arrays with Integrated Readout for Vapor Detection.

This paper reports on the development of an autonomous instrument based on an array of eight resonant microcantilevers for vapor detection. The fabricated sensors are label-free devices, allowing chemical and biological functionalization. In this work, sensors based on an array of silicon and synthetic diamond microcantilevers are sensitized with polymeric films for the detection of analytes. The main advantage of the proposed system is that sensors can be easily changed for another application or for cleaning since the developed gas cell presents removable electrical connections. We report the successful application of our electronic nose approach to detect 12 volatile organic compounds. Moreover, the response pattern of the cantilever arrays is interpreted via principal component analysis (PCA) techniques in order to identify samples.

Natural convection in a cold enclosure with four hot inner cylinders based on diamond arrays (Part-I: Effect of horizontal and vertical equal distance of inner cylinders)

Two-dimensional numerical simulations were conducted to investigate the natural convection heat transfer induced by a temperature difference between the hot surfaces of four inner cylinders and the walls of an enclosure. The simulations were done using different Rayleigh numbers (103≤Ra≤106) and distances between neighboring cylinders (0.3≤ε≤0.7). The immersed boundary method (IBM) was used to capture the virtual boundary of the four cylinders, which we arranged in a diamond array. Detailed analysis results including the distribution of streamlines, isotherms, and Nusselt numbers are presented. The thermal and flow fields reached steady state in the Rayleigh number range of 103≤Ra≤105, regardless of the variation in ε. However, at Ra=106, the numerical solutions show time-dependent characteristics when the distance between neighboring cylinders is 0.4≤ε≤0.6.

Diamond nanostructures for drug delivery, bioimaging, and biosensing.

Diamond features an attractive combination of outstanding mechanical, optical, thermal and electrical properties; tunable surface characteristics; and unprecedented biocompatibility. Additionally, diamond can possess unique nitrogen-vacancy emission centers that are highly photostable and extremely sensitive to magnetic fields, temperatures, ion concentrations, and spin densities. With these inherent merits, diamond in various nanoscale configurations has demonstrated a variety of distinctive applications in a broad range of fields. In particular, research on diamond nanoparticles (0-dimensional structures) and arrays of diamond nanoneedles/nanowires (1-dimensional structures) has witnessed important and exciting progress in recent years. Here, we systematically review the superior properties of diamond nanomaterials and the nitrogen-vacancy centers they contain as well as their uses in biomedical applications, including biosensing, bioimaging and drug delivery. Moreover, systematic studies of the biocompatibility and toxicity of diamond nanostructures, which constitute an important issue for the biomedical applications of diamond that has not yet been thoroughly addressed in previous reviews, are also discussed. Finally, we present our insights into the key issues concerning these diamond nanomaterials and their future development for applications.

Fabrication and characterization of boron doped diamond microelectrode arrays of varied geometry

Boron doped diamond (BDD) is a well-known electrode material that exhibits an excellent electrochemical potential window with very low background current. With this, microelectrodes and microelectrode arrays (MEAs) have been found to even further lower background currents without compromising sensitivity. As such, BDD MEAs are excellent electrode materials for a variety of electroanalytical applications, capable of multi-mode detection. We fabricated BDD MEAs adapting traditional semiconductor microfabrication processes; the resulting MEAs were patterned in different geometries to find an optimum electrochemical response, depending on the application. This is demonstrated using 4 different MEA geometries of different size and spacing using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), where the charge transfer resistance (Rct) increases as the electrodes are farther spaced from one another. Excellent sigmoidal voltammogram shape in CV was obtained for each BDD MEA geometry. BDD MEAs spaced farther from one another were found to give better resolution from the background in fast scan cyclic voltammetric measurements of dopamine due to the decrease in the double layer capacitance (Cdl) as verified with EIS. This work furthers the understanding of BDD MEAs and their pertinence to sensitive electroanalytical techniques.

In-plane elastic responses of circular cell honeycombs and bundled circular tubes in a diamond array structure

Assemblages of circular tubes and circular honeycombs in close packed arrangement are presently both competing and complementing regular honeycomb structures (HCS). The intrinsic isotropy of bundled tubes/rings in hexagonal arrays restricts their use to applications with isotopic need. With the aim of extending the utility of tubes/rings assemblages to anisotropic needs, this paper explores the prospects of bundled tubes and circular honeycombs in a general diamond array structure (DAS) to cater these needs. To this end, effective transverse Young’s moduli and Poisson’s ratio for thick/thin DAS are obtained theoretically. Analysis frameworks including thin ring theory (TRT), curved beam theory (CBT) and elasticity formulations are tested and corroborated by FEA employing contact elements. Results indicate that TRT and CBT are reasonable for thin tubes and honeycombs. Nevertheless, TRT yields compact formulae to study the anisotropy ratio, moduli spectrum and sensitivity of the assemblage as a function of thicknesses and array structure. These formulae supplement designers as a guide to tailor the structures. On the other hand, elasticity formulation can estimate over a larger range including very thick tubes/rings. In addition, this formulation offers to estimate refined transverse strengths of assemblages.

In-plane effective shear modulus of generalized circular honeycomb structures and bundled tubes in a diamond array structure

Use of circular hexagonal honeycomb structures and tube assemblies in energy absorption systems has attracted a large number of literature on their characterization under crushing and impact loads. Notwithstanding these, effective shear moduli (G⁎) required for complete transverse elastic characterization and in analyses of hierarchical structures have received scant attention. In an attempt to fill this void, the present study undertakes to evaluate G⁎ of a generalized circular honeycomb structures and tube assemblies in a diamond array structure (DAS) with no restriction on their thickness. These structures present a potential to realize a spectrum of moduli with minimal modifications, a point of relevance for manufactures and designers. To evaluate G⁎ in this paper, models based on technical theories – thin ring theory and curved beam theory – and rigorous theory of elasticity are investigated and corroborated with FEA employing contact elements. Technical theories which give a good match for thin HCS offer compact expressions for moduli which can be harvested to study sensitivity of moduli on topology. On the other hand, elasticity model offers a very good match over a large range of thickness along with exact analysis of stresses by employing computationally efficient expressions.

(Keynote) Heterogeneous Integration of MEMS by Adhesive Bonding

Technology called microsystems or MEMS (micro electro mechanical systems) has been developed and applied as value added devices for systems. It is based on semiconductor microfabrication integrating not only circuits but also sensors, actuators and microstructures. MEMS as switches and filters fabricated on CMOS LSI are needed for future multi-band wireless systems, in which good mechanical properties or piezoelectric materials are required for the MEMS and state of the art for the LSI. Such heterogeneous integration can be performed by transferring MEMS devices fabricated on a carrier wafer to a LSI wafer by adhesive bonding (Figure). Wafer level selective transfer from one carrier wafer to multiple target wafers are needed for cost-effective integration of different size chips. The selective transfer technology was applied to multiple SAW (surface acoustic wave) resonators on LSI and tunable SAW filter having variable ferroelectric capacitor. Distributed tactile sensors are needed on the skin of robots to ensure their safety in nursing care robots. A tactile sensor network acquires sensing data from each tactile sensor element by autonomous data transmission (event driven). Capacitive tactile force sensors were formed on a communication LSI by adhesive bonding. An electron emitter array integrated with a 100×100 active-matrix driving LSI has been developed using the adhesive bonding. Massive parallel EB (electron beam) exposure systems for maskless lithography (digital fabrication of LSI) are under development. A nc (nanocrystalline)-Si emitter consists of cascaded tunnel junctions can be controlled at low voltage (10V). Resist patterning by the emitted electron was successfully confirmed. Amperometric biosensor in which 20×20 boron doped diamond electrode array are formed on LSI using the adhesive bonding. Distribution of chemicals like neurotransmitter can be detected owing to a wide potential window of the diamond electrode. Cost effective development is required for micro systems because they are versatile and not standardized. A hands-on access fabrication facility in our University is reuse of a production line for power transistor and donated equipments. Companies can easily access and utilize for their prototyping or small-volume production. It is equipped with 4 and 6 inch facilities. The users are charged depending on their amount of usage. They can access a lot of technology and know-how accumulated and can be assisted by skilled engineers. More than 150 companies are using this facility and it is allowed to sell produced small volume devices. Figure 1

Field emission characteristics of diamond nano-tip array fabricated by anodic aluminum oxide template with nano-conical holes

Different sizes and periods of diamond nano-tip arrays are fabricated by anodic aluminum oxide (AAO) template with nano-conical holes. Before the anodic oxidation process, 99.5% Al sheets are annealed and electro-polished. AAO templates with nano-conical holes are obtained by continuously changing voltages from 40 to 160V in 0.3M oxalic acid at the temperature of −3°C. The aluminum pore of AAO is then removed by the wet etching solution of CuCl and HCl. Diamond nano-particles of diameters of 4–12nm are adhered to the AAO template as the nucleation sites by Polyethylenimine method. The diamond nano-tip arrays are deposited on the template by microwave plasma chemical vapor deposition with the mixture gas of methane and argon. The diamond nano-tip array of different sizes and periods are obtained after the AAO template is completely removed by NaOH etching. The ratio of nano-tip spacing to the pitch-height (pitch-height ratio) ranges from 1 to about 2.5. The diamond nano-tip array with the smallest spacing-height ratio of 1 by the AAO template with nano-conical holes has the highest field enhancement factor (β) of 4885 and the lowest turn-on field of about 2.63V/μm.

Tunable configurational anisotropy in collective magnetization dynamics of Ni80Fe20 nanodot arrays with varying dot shapes

We present broadband ferromagnetic resonance measurements of tunable spin wave anisotropy in arrays of nanodots with different dot shapes. Magnetization dynamics of the circular dot array shows two modes, while square, diamond, and triangular dot arrays show three, three, and four modes, respectively. Various distinct rotational symmetries in the configurational anisotropy of the nanodot arrays are observed with the variation of dot shape. The observed spin wave modes are reproduced by micromagnetic simulations and the calculated mode profiles show different collective modes determined by internal and stray magnetic fields. Effects of dot shapes are observed in combination with the effects of lattice symmetry and the shape of the boundary of the array. The collective behaviour is observed to be weakest in the diamond shaped dots and strongest in circular shaped dots. This is further confirmed by the stray field calculation. The large variation of spin wave mode frequencies and their configurational anisotropies with dot shapes are important for selection of suitable basis structures for future magnonic crystals.

Boron doped diamond microelectrodes arrays for electrochemical detection in HPLC

Boron doped diamond microelectrodes arrays (MEA) have been prepared in order to be used as new amperometric sensors in electrochemical cells for HPLC detectors. The following parameters were studied: number and diameter (15–40µm) of the electrodes, distance between them (50–240µm), and effect of the flow rate (0.1–3mL/min). It was thus possible to find the optimum value of the parameters which give a good signal/noise ratio in the chronoamperometric responses, with a size of the electrochemical sensors as small as possible.

Fabrication of periodically ordered diamond nanostructures by microsphere lithography

Structured diamond films are required for several uses as photonic crystals, (bio‐) sensors, biomedicine, etc. Often, these uses require fabrication of nano‐sized features with the assistance of lithographic techniques. In this paper, we demonstrate the growth of diamond structures well ordered in periodic arrays. The technological process starts with ultrasonic seeding of Si substrates by ultra‐dispersed detonation diamond nanoparticles. Then, a monolayer of polystyrene microspheres (PS) is deposited on seeded Si substrates by Langmuir–Blodgett method. The primary diameter of PS varies from 253 to 940 nm. The self‐assembled PS are employed as a mechanical mask for reactive ion etching of the seeding layer via reducing the PS diameter down. The seeding structures remained under reduced PS were used for growing periodically ordered diamond arrays by microwave plasma‐assisted chemical vapor deposition from a hydrogen rich gas mixture. Cross‐section SEM images reveal that the diameter and size of the formed diamond structures increase both in vertical and lateral direction. At a certain deposition time, the structures start to coalesce into a continuous layer.

Development of a templated approach to fabricate diamond patterns on various substrates.

We demonstrate a robust templated approach to pattern thin films of chemical vapor deposited nanocrystalline diamond grown from monodispersed nanodiamond (mdND) seeds. The method works on a range of substrates, and we herein demonstrate the method using silicon, aluminum nitride (AlN), and sapphire substrates. Patterns are defined using photo- and e-beam lithography, which are seeded with mdND colloids and subsequently introduced into microwave assisted chemical vapor deposition reactor to grow patterned nanocrystalline diamond films. In this study, we investigate various factors that affect the selective seeding of different substrates to create high quality diamond thin films, including mdND surface termination, zeta potential, surface treatment, and plasma cleaning. Although the electrostatic interaction between mdND colloids and substrates is the main process driving adherence, we found that chemical reaction (esterification) or hydrogen bonding can potentially dominate the seeding process. Leveraging the knowledge on these different interactions, we optimize fabrication protocols to eliminate unwanted diamond nucleation outside the patterned areas. Furthermore, we have achieved the deposition of patterned diamond films and arrays over a range of feature sizes. This study contributes to a comprehensive understanding of the mdND-substrate interaction that will enable the fabrication of integrated nanocrystalline diamond thin films for microelectronics, sensors, and tissue culturing applications.

Preparation and characterization of vertically columnar boron doped diamond array electrode

A vertically columnar boron doped diamond (BDD) array electrode was fabricated by microwave plasma chemical vapor deposition. Observed by scanning electron microscopy, the fabricated samples were structured with aligned columns whose diameter and height was 8μm and 12μm, respectively, and the minimum interval of neighboring columns was 2μm. The results of electrochemistry measurement showed that the columnar BDD array electrode possessed high oxygen evolution potential and low background current. Besides that, comparing with flat BDD electrode, the columnar BDD array electrode showed higher electrochemical activity (due to its inner active surface being up to 4.25cm2), lower impedance of electric double layer, and especially enhanced electrical response signal (2.12μA/μM, 4 times of flat BDD in glucose detection as a sample). These excellent performances may open the door for the BDD materials to be applied in wide areas including electrochemical detection, electrochemistry degradation, electrochemical synthesis, and so on.

Wideband Circularly Polarized SIW Antenna Array That Uses Sequential Rotation Feeding

A wideband right-handed circularly polarized (CP) substrate integrated waveguide- (SIW-) based diamond ring-slot antenna array at the X-band is presented in this study. The array consists of four elements that exhibit wideband impedance matching characteristics and good radiation performance. The array also employs a sequential rotation feeding method to achieve the wideband axial ratio (AR) bandwidth. The feeding network is based on the SIW power divider with a delay line related to sequential rotation feeding. To validate our design, an antenna array is fabricated and measured. The measured impedance and AR bandwidths are 19.2% (VSWR<2) and 14.1% (AR<3 dB), respectively. Moreover, the antenna has a stable CP peak gain of more than 12 dBic from 10.1 GHz to 10.7 GHz.

Synthesis and Field Emission Properties of Diamond Microcrystalline-Aggregate Array

The diamond microcrystalline-aggregate array was fabricated by microwave plasma chemical vapor deposition (MPCVD) method. The ceramic with a Ti mental layer is used as substrate. The diamond array was evaluated by Raman scattering spectroscopy, x-ray diffraction spectrum (XRD), scanning electron microscopy (SEM). The field emission properties were tested by using a diode structure in a vacuum. A phosphor-coated indium tin oxide (ITO) anode was used for observing and characterizing the field emission. It was found that the diamond microcrystalline-aggregate array exhibited better electron emission properties. The turn-on field is only 1.1V/μm and a emission current density as high as 1mA/cm2 was obtained under an applied field of 3.3V/μm. The good field emission properties of the diamond microcrystalline-aggregate array are discussed relating to microstructure and electrical conductivity.

SECM detection of single boron doped diamond nanodes and nanoelectrode arrays using phase-operated shear force technique

Boron doped diamond (BDD) is a promising electrode material for electrochemical biosensor applications due to its low bio-fouling, chemical stability, and large potential window. For the first time, BDD nanoelectrode arrays (NEA) were studied using Scanning Electrochemical Microscopy (SECM) measurements. Using the phase-operated shear force technique and feedback mode, it was possible to scan a platinum (Pt) nanode with an active radius of 167nm over a diamond array at a constant distance of 45nm and to detect the electrochemical activity of single BDD nanodes in the 100nm range.

Fabrication and structural property of diamond nano-platelet arrays on {111} textured diamond film

Diamond nano-platelet (DNP) arrays have been grown on {111} textured diamond film by using micro-wave plasma enhanced chemical vapor deposition system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize the growth behavior and micro-structure of DNP arrays on diamond film. According to the results of SEM and TEM images, DNP arrays only appear on the {111} surfaces of underlying diamond grains. Both DNPs and underlying diamond grains comprise penetration {111} twin structures. The growth of DNPs is the extension of the penetration {111} twins from underlying diamond grains. The accommodation and glide of stacking faults can also evolve into perfect {111} twin structures during the growth of DNPs.

Nanograss array boron-doped diamond electrode for enhanced electron transfer from Shewanella loihica PV-4

The inhibited electron transfer from electricigens to the electrode is one of the main limitations for the performance of microbial fuel cells (MFCs). This study compares catalytic current generation and electrochemical behavior of Shewanella loihica PV-4 on boron-doped diamond (BDD) and nanograss array BDD electrode in an electrochemical cell. Experimental results show that the good biocompatibility and electron transportation ability of nanograss array BDD greatly improve the direct electron transfer and can make it suitable for the anode of high performance MFC.

Suppressed Screening Effects in Curvilinear Tetrahedral Diamond Field Emitter Arrays Fabricated on Anodic Aluminum Oxide

Curvilineary tetrahedral diamond arrays of nano-tip with different pitches are firstly fabricated and the suppressed screening effects are also investigated. The curvilinear tetrahedral diamond arrays are fabricated by hot-filament chemical vapor deposition (HFCVD) on anodic aluminum oxide (AAO) template. The AAO template is fabricated by hard anodization. The diamond nano-particles are adhered onto the barrier layer of AAO template by Polyethylenimine pretreatment to increase the nucleation density of diamond. The diamond film is then deposited on the barrier layer of AAO by HFCVD. Curvilinear tetrahedral diamond arrays of nano-tip are developed after the removal of AAO template by wet chemical etching. The field emission effects of different diamond nano-tip arrays are measured by field emission meter. The morphology and quality of curvilinear tetrahedral diamond nano-tip array are examined by scanning electron microscopy and Raman spectroscopy, respectively. Innovative curvilinear tetrahedral structures are obtained successfully with the tip radius of 15 nm-30 nm, and the height of 100 nm-200 nm at different pitches from 50 nm to 300 nm. As a result, the lowest turn-on electric field of 5.4 V/μm and the highest field emission current density of 8.4 μA/cm2 can be obtained at the smallest pitch-height ratio of 0.25-1 without screening effect.

Pressure Loss and Heat Transfer Through Heat Sinks Produced by Selective Laser Melting

Heat removal from electronic packages is often assisted with the use of heat sinks whose heat transfer surfaces come in a variety of forms such as cylindrical pins, flat fins, and corrugated sheet. These conventional designs are manufactured by traditional methods such as forging, machining, casting, stamping and bending, or a combination of processes. This article introduces a novel manufacturing technique, selective laser melting (SLM), and demonstrates its ability to fabricate new designs of heat sink that have not previously been considered, primarily due to their geometric complexity. Three novel finned structures have been manufactured and their thermal and fluid flow characteristics have been determined experimentally. The three heat sinks demonstrate selective laser melting's ability to produce fine detail and consist of a staggered elliptical array, an elliptical array where the pins are angled in a direction perpendicular to the flow, and a densely packed diamond array. The novel heat sink designs were compared to a cylindrical pin array manufactured using the SLM process as well as with pin fin data from the literature. The heat sinks produced by the SLM method have been shown to have superior performance to that of the conventional heat sinks. Although the angled elliptical fins transmit similar amounts of heat to the cylindrical pin fins across the range of air flow rates considered, they incur a lower pressure loss. The densely packed diamond array not only transfers 60% more heat than the cylindrical array, but does so with a lower pressure drop across it.