Nanodiamonds (NDs) represent a novel nanomaterial applicable from biomedicine to spintronics. Here we study ability of air annealing to further decrease the typical 5 nm NDs produced by detonation synthesis. We use atomic force microscopy (AFM) with sub-nm resolution to directly measure individual detonation nanodiamonds (DNDs) on a flat Si substrate. By means of particle analysis we obtain their accurate and statistically relevant size distributions. Using this approach, we characterize evolution of the size distribution as a function of time and annealing temperature: i) at constant time (25 min) with changing temperature (480, 490, 500°C) and ii) at constant temperature (490°C) with changing time (10, 25, 50 min). We show that the mean size of DNDs can be controllably reduced from 4.5 nm to 1.8 nm without noticeable particle loss and down to 1.3 nm with 36% yield. By air annealing the size distribution changes from Gaussian to lognormal with a steep edge around 1 nm, indicating instability of DNDs below 1 nm.

We investigated the fabrication of diamond-like carbon (DLC) emitter patterns by room-temperature curing nanoimprint lithography (RTC-NIL) with polydimethylsiloxane (PDMS) molds using polysiloxane, as an application to the emitter for the next generation flat panel display.

The DLC which has excellent properties similar to diamond properties was used as a pattern material. A PDMS was used as a mold material and fabricated by the following optimum conditions of the first curing time at RT for 36 h and the second curing time at the temperature of 150 °C for 15 mins. The polysiloxane is in the state of sticky liquid at RT and stable in air. Therefore, the polysiloxane was used the electron beam (EB) resist and oxide mask material in EB lithography, and also used as RT-imprint material.

First, we fabricated the PDMS mold with pit array. Each dot is 5 µm-diameter and 400 nm-depth. We carried out the RTC-NIL process with PDMS molds using polysiloxane under the following optimum imprint conditions of 0.5 MPa-imprinting pressure, 1.5 min-the time between spin-coat and imprint, and 5 min-imprinting time. Next, the residual layer of imprinted polysiloxane pattern was 450 nm and then was removed with electron cyclotron resonance (ECR) trifluoromethane (CHF3) ion shower under the conditions of 300 eV-ion energy and 3 min-etching time. Then, we processed the imprinted polysiloxane patterns on the DLC film with an ECR oxygen (O2) ion shower under the conditions of 400 eV-ion energy and 12 min-etching time. As a result, we succeeded in fabricating convex DLC emitter patterns with high accuracy which has 5 µm-diameter and 500 nm-height.

Secondary electron transmission measurements are used to examine the electron diffusion and thermalization processes in B-doped nanocrystalline diamond membranes of thickness 2.3 μm and 650 nm. Specifically, transmitted energy spectra are measured following impact by an electron beam that penetrates deeper in the membrane as the beam energy Eo increases. A fully-thermalized emission peak is observed for Eo ≤ 16 keV and Eo ≤ 7 keV from the 2.3-μm-thick and 650-nm-thick films, respectively, with a small high-energy tail beginning to emerge at higher Eo. These measurements are analyzed using Monte Carlo simulations that generate constant-energy contour lines (down to 0.05 Eo) as a function of beam depth into the film. From these simulations, we deduce that secondary electrons have a minimum thermalization length of ∼ 630 nm and ∼ 260 nm in the 2.3-μm-thick and 650-nm-thick films, respectively. Further insight into the secondary-electron transport behavior is gained from the analysis, and this understanding is applied to the design of a transmission electron-current amplifier device.

Boron doped nanocrystalline diamond films (BDND) were grown on reticulated vitreous carbon (RVC) heat treated at 1000 and 1700 °C. Silver (Ag) nanoparticles were electrodeposited on RVC and RVC/BDND composites by potentiostatic reduction of AgNO3 solution. The samples were characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and cyclic voltammetry. The samples conductivities influenced the Ag deposition amount as well as the Ag particle sizes where the smaller Ag particles were observed for RVC/BDND composites. The stability of Ag nanoparticles was also confirmed by cyclic voltammetry.

An investigation of the electronic structure of charged vacancies and X(C), X=(As, Sb, P) substitutional centers in diamond has been carried out by means of ab initio density functional theory. The revised Heyd-Scuseria-Ernzerhof screened hybrid functional (HSE06) was utilized for the total energy calculation. The equilibrium geometry, defect charge transition levels and energetics of the vacancies and substitutional centers were determined. It is found that substitutional As and Sb introduce a donor level into the band gap about 0.5 eV with respect to the conduction band minimum (CBM), therefore, these elements may be a good choice for achieving n-type diamond. From a technological point of view, however, fabrication of As and Sb doped diamond would be challenging due to its high, positive formation energy.

The performance of new type three dimensional buried-in electrode structure ultraviolet photodetector fabricated on single crystal diamond epitaxial layer was investigated. The epitaxial layer was grown on high-pressure-high-temperature Ib-type diamond substrate. Then the buried-in electrodes with different depths were formed by oxygen plasma reactive ion etching method and radio frequency magnetron sputtering technique on this diamond layer. Compared with that of traditional planar electrode photodetector, the responsivity of buried-in electrode photodetector shows higher value, which reaches the highest when the electrode depth is 100 nm.

Atomic force microscopy (AFM) is used to measure local electrical conductivity of HPHT nanodiamonds (NDs) dispersed on Au substrate in the as-received state and after thermal or plasma treatments. Oxygen-treated NDs are highly electrically resistive, whereas on hydrogen-treated NDs electric current around -200 pA at -2 V is detected. The as-received NDs as well as NDs after an underwater radio-frequency (RF) plasma or laser irradiation (LI) treatments contain both electrically conductive (two types: highly and weakly conductive) and highly resistive particles. The higher conductivity is attributed to H-terminated (RF) or graphitized (LI) NDs. The lower conductivity is attributed to NDs with hydrogenated amorphous carbon shell.

Diamond stands out among single-photon sources due to an intrinsically large band gap, photo-stable emission, room-temperature operation, short excited state lifetimes, and the ability to host hundreds of different color centers. Currently, most of these centers are active in the optical spectrum, but a single-photon source in the infrared would represent a significant advancement. In pursuit of this end, a number of different transition metal atoms have been studied as dopants in the diamond lattice via the GAMESS (General Atomic Molecular and Electronic Structure System) cluster calculation package. The importance of cluster size and electron correlation effects is considered, and excitation energies have been calculated via time-dependent density functional theory.

We investigated the fabrication of convex diamond-like carbon (DLC) based microgears in room-temperature curing nanoimprint lithography (RTC-NIL) using the ladder-type hydrogen silsesquioxane (HSQ), as an application for the medical micro electro mechanical system (MEMS). The HSQ which is an inorganic polymer of sol-gel system turns into a gel when exposed to air and has the siloxane bond. Therefore, the HSQ was used as RT-imprinting material, and also used as an oxide mask material in electron cyclotron resonance (ECR) oxygen (O2) ion shower etching. We fabricated the polydimethylsiloxane (PDMS) mold with concave microgear patterns which has 40, 50 and 60 μm-tip diameter and 300 nm-depth. We carried out the RTC-NIL process using the PDMS mold under the following optimum conditions of 0.10 MPa-imprinting pressure and 1.0 min-imprinting time. We found that the residual layer of imprinted HSQ microgear patterns was removed with ECR trifluoromethane (CHF3) ion shower under the following conditions of 300 eV-ion energy and 2.0 min-etching time, and then microgears of the HSQ on the DLC film were etched with ECR O2 ion shower under the following conditions of 400 eV-ion energy and 10 min-etching time. As a result, the convex DLC based microgears which have 40, 50 and 60 μm-tip diameter and 400 nm-height were fabricated with high accuracy in the new fabrication process of RTC-NIL.

Schottky properties of Mo on diamond with fluorine- and oxygen-termination had been investigated. Oxygen-termination was generated by aqua regia. Fluorine-termination was generated by CF4 plasma treatment. Mo/Ni/Au was deposited on the diamond surface as Schottky electrode, whose barrier height was evaluated from current-voltage curve. After that, the X-ray photoelectron spectroscopy methods were applied to calculate the Schottky barrier height of Mo on different termination surface. The results indicated that the fluorine-termination and oxygen-termination show different schottky properties.

Boron Doped Diamond (BDD) electrodes exhibit excellent properties including a wide potential window in aqueous media, high corrosion resistance, chemical inertness, bio-compatibility and low background current. In order to increase their selectivity for analytical applications, several studies were carried out recently on the possibility to deposit metal nanoparticles such as Pt or Ir on such BDD electrodes1,2,3,4. Indeed these nanoparticles bring interesting electro-catalytic properties to the electrodes, thus offering the possibility to address new analytes. Here an electrode array was developed, based on multiple BDD electrodes casted with various metal nanoparticles. The simultaneous detection of analytes by each electrode composing the array gives potentially a unique fingerprint to the analytes, thus increasing the specificity and the selectivity of the sensor.