Diamond Diode Research Articles

Surface transfer doped diamond diodes with metal oxide passivation and field-plate

Surface transfer-doping, involving hydrogen terminated diamond surfaces, has been an effective method for producing diamond devices for some years but suffered from poor device longevity and reproducibility. The emergence of metal oxides as an encapsulant has begun to change this situation. Here, HfO2 encapsulated surface transfer doped diamond Schottky diodes with stable device characteristics have been demonstrated. Ideality factor and Schottky barrier heights of the devices did not vary considerably across extended periods of use (up to 39 days). The devices showed excellent blocking capabilities, demonstrating no catastrophic breakdown under the maximum field applied and only a slight increase in leakage current at the reverse bias and field strength of 200 V and 0.167 MV cm−1, respectively. Indeed, a large rectification ratio of up to 108 and a very low leakage current of ≈10−9 A cm−1 were maintained at this reverse bias (200 V). Furthermore, multiple devices were compared across a single substrate, something rarely reported previously for surface transfer doped diamond diodes. Leakage currents and rectification ratios were similar for all of the devices.

1651-V All-Ion-Implanted Schottky Barrier Diode on Heteroepitaxial Diamond With 3.6 × 10⁵ On/Off Ratio

In this letter, we have reported a lateral diamond Schottky barrier diode (SBD) that was fabricated on a heteroepitaxial diamond substrate using all ion-implantation processes. The SBD exhibited a lower reverse leakage current, which resulted in an unprecedentedly high rectification ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.6\times 10^{{5}}$ </tex-math></inline-formula> when compared to ion-implanted diamond diodes. The reverse breakdown voltage was measured to be 1.65 kV- the highest measurement ever reported among ion-implanted diamond devices. In addition, the ideality factor and Schottky barrier height were determined as 4.9 and 1.4 eV, respectively, under the forward bias conditions. This study revealed the improvement of ion-implanted diamond SBD by using high-quality heteroepitaxial diamond substrates and low channel doping concentration.

Dosimetric characterization of a novel commercial plastic scintillation detector with an MR-Linac.

Plastic scintillators have been used as radiation detectors for the past few years, as they are water-equivalent and independent of the dose, dose rate, and angle of incidence. In addition, they are also independent of the presence of a magnetic field and could be used for in vivo dosimetry in an MR-Linac. With the advent of a new commercial scintillation detector, Blue Physics Model 10, its characterization has been performed on an MR-Linac with a view to future applications. To perform the dosimetric characterization and study potential applications of a novel commercial plastic scintillation detector in a MR-Linac. Scintillation detector description, calibration procedure, short-term repeatability, dose-response linearity, dose-rate dependence, angular dependence, and temperature dependence have been studied. Percent-depth-dose (PDD) and beam profiles were measured for small fields and a standard field, as well as output factors, for comparison with other PTW detectors: a diamond diode and PinPoint and Semiflex 3D ionization chambers. The suitability of the plastic scintillator for in vivo dosimetry in a magnetic field has also been studied measuring the dose to a point in an anthropomorphic phantom while acquiring MR imaging. This measured dose was compared with that calculated with Monaco planning system and with that measured with a PTW Semiflex 3D chamber, the latter without acquiring MR images. Short-term repeatability presented negligible variations (<0.4%) for 100 and 20 MU. Similar results were obtained for dose-response linearity and dose-rate dependence. A small angular dependence was determined, while the scintillator resulted practically independent of the temperature. PDDs showed excellent agreement except in the build-up region, and calculated penumbras with the profiles given by the scintillator were between the ones obtained with the diamond detector and the PinPoint ionization chamber. Measured OF with the scintillator were the highest between all detectors, 1.26% higher than the value obtained with the microdiamond for the smallest field measured, 0.5×0.5cm2 . Finally, the total dose to a point measured with the scintillator was 0.51% higher compared to that calculated by the planning system. The Blue Physics model 10 scintillation system showed excellent dosimetric characteristics. Its response independent of the temperature and the presence of a magnetic field make it suitable for in vivo dosimetry in an MR-Linac while acquiring MR images, which could solve the impossibility of performing a dosimetric QA for each adapted plan. Furthermore, its temporal resolution allows independent radiation pulses to be measured and visualized, which could be used in future applications.

High-power diamond diodes tested with electronic noise

Characterizing defects in diamond devices destined for high-power electronics

Excess noise in high-current diamond diodes

We report the results of an investigation of low-frequency excess noise in high-current diamond diodes. It was found that the electronic excess noise of the diamond diodes is dominated by the 1/f and generation-recombination noise, which reveals itself as Lorentzian spectral features (f is the frequency). The generation-recombination bulges are characteristic of diamond diodes with lower turn-on voltages. The noise spectral density dependence on forward current, I, reveals three distinctive regions in all examined devices—it scales as I2 at the low (I &amp;lt; 10 μA) and high (I &amp;gt; 10 mA) currents and, rather unusually, remains nearly constant at the intermediate current range. The characteristic trap time constants, extracted from the noise data, show a uniquely strong dependence on current. Interestingly, the performance of the diamond diodes improves with the increasing temperature. The obtained results are important for the development of noise spectroscopy-based approaches for device reliability assessment for high-power diamond electronics.

ДВУСЛОЙНЫЕ ПЛАСТИНЫ ИЗ СИНТЕТИЧЕСКИХ МОНОКРИСТАЛЛОВ АЛМАЗА, ЛЕГИРОВАННЫХ АЗОТОМ, ДЛЯ ВЫСОКОТЕМПЕРАТУРНЫХ ДИОДОВ ШОТТКИ n-ТИПА

For the first time, a vertical Schottky diamond diode with an electronic type of conductivity was manufactured and investigated on the basis of a two-layer single-crystal plate of synthetic diamond doped with nitrogen, in which a thin working layer of low-nitrogen-doped diamond was grown by the chemical vapor deposition method homoepitaxially on a heavily nitrogen-doped substrate cut in the plane {100} from a single crystal grown by the method of high-pressure-high-temperature growth on the seed. The concentration of nitrogen in the form of single substitution atoms (C-centers) in the working layer, grown by the chemical vapor deposition method, was 0.5 ppm, the layer thickness was 10 μm, the thickness of the substrate with a nitrogen concentration of ~ 200 ppm was 400 μm. 6 Schottky contacts with a diameter of 0.6 mm were made by magnetron sputtering of a platinum layer with a thickness of 200 nm through a contact mask. A rectangular ohmic contact was made to the substrate also by magnetron sputtering through a contact mask of a 5 nm thick Ti layer, followed by high-temperature annealing in vacuum to form titanium carbide, and subsequent deposition of a Pt layer with a thickness of 200 nm to prevent oxidation of titanium carbide in air. The current-voltage characteristics of the manufactured diodes were studied at a bias range of (-200 V) – (+200) V at temperatures up to 650 °C. The opening voltage of the manufactured diode structure is ~ 30 V, the maximum current of each diode in the open state reaches 1 mA at U = 200V, while the reverse current at T = 525-650 °C does not exceed 0.1 µA. The highest rectification coefficient value was ~104.

Demonstration and Analysis of Ultrahigh Forward Current Density Diamond Diodes

A diamond Schottky p-i-n diode (SPIND) with the highest reported current density to date of ~116 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is demonstrated, carrying a total current of ~1.32 A through a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50-\mu \text {m}$ </tex-math></inline-formula> wide pseudo-vertical diode structure. The diamond SPIND also provides a maximum power handling capacity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.85}~ \text {MW/c}\text {m}^{{2}}$ </tex-math></inline-formula> and a low specific ON-resistance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ \mathrm{ON}}S$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${0.05}~ \text {m}\Omega \cdot \text {cm}^{{{2}}}$ </tex-math></inline-formula> at a forward bias of ~16 V. The diamond Schottky p-i-n (SPIN) diode also shows excellent rectification characteristics with a current ON– OFF-ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim {6} \times {10}^{{12}}$ </tex-math></inline-formula> . An analytical model including thermionic emission and space charge limited (SCL) current is presented together with Silvaco ATLAS Technology Computer Aided Design (TCAD) simulations to accurately reproduce the experimental <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> characteristics using multiple single-trap levels and other physical models emulating a real device. Theoretical calculations from the analytical model show that further improvement in the device turn on voltage and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{ \mathrm{ON}}{S}$ </tex-math></inline-formula> can be achieved by reducing the defect density and contact resistance in order to approach the ultimate performance in the Mott–Gurney SCL current regime.

Distinguishing dislocation densities in intrinsic layers of pin diamond diodes using two photon-excited photoluminescence imaging

The density of dislocations that occur in the intrinsic (i-) layer of a pin diamond diode was estimated from two-photon excitation photoluminescence (2PPL) imaging. Results elucidated data obtained from device characteristic measurements and cathodoluminescence (CL). Generation and diffusion of free carriers for deep-level emission in the i-layer have no effect on emission images observed using the 2PPL method. Therefore, to evaluate the pin diode structure, the influence of free carrier propagation on the adjacent layer can be avoided. However, this effect cannot be ignored when using CL. These findings are expected to be important for assessing diamond device performance.

Study of frequency dispersion of capacitance-voltage characteristics of boron-doped diamond Schottky diodes

A single-crystal diamond doped with boron was studied in this work. For electrical measurements an array of Schottky contacts and a large Ohmic contact were fabricated. The capacitance-voltage (C-V) characteristics of the sample were obtained experimentally in wide temperature range and modeled. At high temperature (445 K) the slope of the C-V characteristics does not depend on the test signal frequency. The calculated concentration of free charge carriers is the same for all frequencies within the experimental error and approximately corresponds to the total boron concentration. At low temperatures (235 K), there is a significant difference in capacitances measured at different frequencies, the calculated concentration varies from 5·1017 cm-3 to 5·1015 cm-3 in the available frequency range. The reasons for the frequency dispersion of capacitance-voltage characteristics of boron-doped diamond diodes are discussed.

Fabrication of Dual-Barrier Planar Structure Diamond Schottky Diodes by Rapid Thermal Annealing

Fabrication of dual-barrier planar (DBP) structure diamond Schottky barrier diodes (SBDs) with only Ni Schottky contact was carried out by rapid thermal annealing. Ni/Au narrow stripes were first patterned on $\text{p}^{-}$ layer and annealed at 550 °C to decrease Schottky barrier height and form low barrier contact. Then, Ni/Au Schottky electrodes were deposited on the window area between stripes to serve as high barrier contact. Ti/Pt/Au ohmic contact was formed on the back side of $\text{p}^{+}$ diamond substrate. The fabricated DBP structure SBDs exhibit low forward voltage drops compared with single high barrier diode, and reverse leakage current densities of two to three orders of magnitude smaller than that of single low barrier diode. The influence of stripes area proportion on device properties was investigated and the barrier height can be adjusted by changing dual-barrier ratio. This new device structure displays a small power dissipation of 0.54 W/cm2, which is a promising technology for high power diamond diodes.

Diamond avalanche diodes for obtaining high-voltage pulse with subnanosecond front edge

In this Letter, we report on demonstrating diamond avalanche diodes for obtaining a high-voltage pulse with a subnanosecond front edge. Under a 2.5 kV driving pulse, the diamond avalanche diodes show a 2.04 kV output and the front edge is 0.894 ns. After repetitive tests, the output voltage wave remains almost the same, indicating good stability. By applying a reverse DC 100 V bias, the front edge shortens to be 0.675 ns, while the rectifier characteristics degrade and the output voltage is limited. Therefore, the reverse bias should be optimized to obtain both the fast front edge and high output voltage. The results show that diamond avalanche diodes have a promising application for high-voltage pulse sources.

Schottky Barrier Height Analysis of Diamond SPIND Using High Temperature Operation up to 873 K

In this work, the high temperature performance of a diamond Schottky PIN diode is reported in the range of 298-873 K. The diamond diode exhibited an explicit rectification up to 723 K with an excellent forward current density of >3000 A/cm 2 . The stability of the diode was investigated by exposing the sample to high temperature cycles (up to 873 K) for more than 10 times (totaling up to 120 hours), which exhibited no change between the I-V characteristics measured in each cycle. The dependence of ideality factor and Schottky barrier height on temperature along with an extracted Richardson's constant much smaller than the theoretical value (0.0461 A/cm 2 .K 2 ), motivated us to study the possible reason for this anomaly. A modified thermionic emission model following Tung's analysis was used to explain the experimental observations. The model assumed the presence of inhomogeneous Schottky barrier heights leading to a reduced effective area and yielded a Richardson's constant closer to the theoretical value. Conductive atomic force microscopy studies were conducted, which concurred with the electrical data and confirmed the presence of inhomogeneous Schottky barrier heights.

Electrical contact considerations for diamond electron emission diodes

The demonstration of diamond devices has substantiated the superior capability of diamond in high power electronics that relied on the preparation of p-type and n-type diamond through boron and phosphorus doping, respectively, and the growth of high purity intrinsic diamond. We present an approach for electrical contacts to homoepitaxial, phosphorus doped, n-type, diamond that utilizes an interfacial layer of highly nitrogen doped, nanostructured carbon grown by plasma enhanced CVD (PECVD). This contact strategy was utilized in a pin diamond diode for electron source applications. The pin-nano-carbon structure was prepared on HPHT type IIb (111) oriented substrates with intrinsic, n-type, and nano-carbon layer grown in dedicated PECVD systems. The nanostructured nitrogen doped carbon layer was synthesized under argon addition to promote re-nucleation. Diodes from this pin-nano-carbon structure were prepared by lithography and mesa-etched devices contacted by Ti/Pt/Au metallurgy. Final processing in a hydrogen plasma established negative electron affinity properties for electron emission. Electrical characterization of the diodes commenced in vacuum after annealing at ~600 °C for 15 min and observation of exciton light emission indicated bipolar transport. At a forward bias of 14 V a current of 0.1A was measured and at 17 V its increase to 0.5A corresponded to a current density >1500 A/cm2. Compared to conventional pin diodes, the introduction of the nano-carbon layer enhanced the diode and electron emission current by more than an order of magnitude. This was attributed to the reduced contact resistivity of 5.5 × 10−3 Ω cm2 at room temperature. Light emission and diode operation at temperatures >750 °C indicated superior stability of the electrical contact. The n-type layer was characterized by SIMS indicating a phosphorus incorporation of ~2 × 1019cm-3 and for the nano-carbon layer a nitrogen incorporation of ~5 × 1020cm−3. Addressing contact limitations to n-type diamond through the growth of moderately phosphorus doped epilayers followed by highly nitrogen doped nano-carbon layers could provide a preferred approach for electronic devices that could also be extended to (100) surfaces.

(Invited) Diamond Technology – Integration into Solid-State Breakers and Biomedical Devices

A commercial viable solid-state direct current circuit breaker with fast switching performance for the use in the 1-100kV range requires a low loss on-resistance close to commercial available mechanical breakers [1]. Diamond provides excellent semiconductor properties for those breaker applications with a material characteristics superior in high electric field breakdown strength, higher thermal conductivity, and high charge carrier mobility as compared to silicon, silicon carbide, and gallium nitride [2-4]. These properties will enable diamond electronic devices that will be more energy efficient while keeping the active area of devices to lower values, which offers a potential cost advantage in case of a better availability of large-area substrates [5,6]. Diamond diodes [7-9], diamond field effect transistors [10], and gate turn-off thyristor devices [11-13] are proposed to be the core unit in a medium voltage direct current (MVDC) solid-state circuit breaker [14,15]. A reduced energy loss in solid-state breakers by using diamond will enable a competitive placement of diamond breakers on the MVDC market with a decisive advantage of a much faster response to electrical circuit faults and more robust DC electrical energy delivery systems with >1MW capacity. The diamond-based diode and FET development focuses on devices in the 1-5kV range and the diamond thyristors cover a 15-20kV range. Higher voltages would ultimately be achieved with series circuit arrangements of the diamond devices. Diamond offers also excellent properties for applications in the biomedical sector [16]. The manufacturing of tailored biopharmaceuticals, stem cells, or human tissue is being attempted through the utilization of single-use perfusion bioreactors due to its minimal spacial and financial costs, and its ability to execute critical parallel processing methods [17,18]. However, continuous monitoring of analytes in multifaceted protein mixtures and achieving full automation of production are challenges inhibiting commercialization of tailored products to a reasonable price. Constant and instantaneous monitoring of a bioreactor both ensures flexibility with the opportunity for quick adjustments and eliminates contamination risks from manual sampling. Also, it is essential that the bioactive layer of an integrated biosensor monitoring system sustains the lifetime of the processing cycle, as well as display a shelf life compatible with standard inventory consumption. Achieving and maintaining the specific conditions necessary to produce complex bio-products requires a robust real-time monitoring with redundancy and automated control of a variety of nutrients, intermediate metabolites, and cell products within the bioreactor. Diamond biosensors exhibit low biofouling rates and show promising results in the in-situ monitoring of the bioprocess conditions for the full operation time of single-use bioreactors [19]. Operational human IL-8 antibodies have been successfully adhered to the diamond sensor surface [20]. A high antibody concentration and activity as a measure of biosensor sensitivity is obtained using a modified ELISA procedure. The results indicate a reasonable robust diamond biosensor performance suitable for in-situ applications in the complex environment of bioreactors [21]. Song, C. Peng, A.Q. Huang (2017) IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS 5(1), 278.Kalish (2007) Journal of Physics D: Applied Physics 40(20), 6467.Hiraiwa, H. Kawarada (2013) Journal of Applied Physics 114(3), 034506.Tsao et.al. (2018) Advanced Electronic Materials 4(1), 1600501.Friel et.al. (2019) Diamond and Related Materials 18, 808.Tallaire, J. Achard, F. Silva, O. Brinza, A. Gicquel (2013) Comptes Rendus Physique 14, 169.Alvearez, M. Boutchich, J. P. Kleider, T. Teraji, Y. Koide (2014) J. Phys. D: Appl. Phys. 47, 355102.Ozawa et.al. (2018) Diamond and Related Materials 85, 49.Zimmermann et.al. (2005) Diamond & Related Materials 14(3-7), 416.Huang, B. Zhang (2000) Solid-State Electronics 44, 325.Paques et.al. (2011) IEEE Electron Device Letters 32, 1421.HERLET, K. RAITHEL (1966) Solid-State Electronics 9, 1089.ADLER (1978) IEEE TRANSACTIONS ON ELECTRON DEVICES ED-25(1), 16.Shenai (2018) IEEE TRANSACTIONS ON ELECTRON DEVICES 65(10), 4216.Gu, P. Wheeler, A. Castellazzi, A.J. Watson, F. Effah (2017) Energies 10, 495.Hébert, S. Ruffinatto, P. Bergonzo (2015) Carbon for Sensing Devices, 978-3-319-08648-4, 227.Shukla, U. Gottschalk (2013) Trends in Biotechnology 31(3), 147.Bijonowski, W.M. Miller, J.A. Wertheim (2013) Current Opinion in Chemical Engineering 2(1), 32.Bixler, B. Bhushan (2012) Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, 2381.Navas et.al. (2018) Applied Surface Science 433, 408.Mross, T. Zimmermann, N. Winkin, M. Kraft, H. Vogt (2016) Sensors and Actuators B: Chemical 236, 937.

Neutralizing the polarization effect of diamond diode detectors using periodic forward bias pulses

A new technique for neutralizing the polarization effect of diamond detectors has been demonstrated. The technique, which relies on the diamond detector to be configured as a diode, is to periodically pulse the diamond diode with forward bias. A 210Po alpha source was used to induce the polarization effect for a thin PIN diamond radiation detector. Results show that for a single forward bias pulse, a forward current of about 60 nA applied for 1 s removes the polarization buildup. The benefits of using this technique add significant value to the diamond diode configuration.

Diamond photovoltaic radiation sensor using pn junction

Because of its heat resistance and radiation hardness, diamond is a suitable semiconductor material for use in radiation sensors operating under harsh environments. To date, diamond radiation sensor designs have been constrained to Metal–Insulator–Metal structures. Instead of this structure, the pn junction offers several advantages for radiation sensors such as high built-in bias, electric field control, and depletion layer thickness control through doping profile design. We formed diamond pn diodes with ideal electric properties. A large built-in bias of 4.7 eV was obtained. The diode represented less than 10−11 A of low leakage current up to nearly 1 MV/cm of a high electric field. We detected alpha particles at zero-bias voltage using the pn diode, which opens the possibility of realizing compact radiation sensors.

Development, commissioning, and evaluation of a new intensity modulated minibeam proton therapy system.

To invent, design, construct, and commission an intensity modulated minibeam proton therapy system (IMMPT) without the need for physical collimation and to compare its resulting conformity to a conventional IMPT system. A proton therapy system (Hitachi, Ltd, Hitachi City, Japan; Model: Probeat-V) was specially modified to produce scanned minibeams without collimation. We performed integral depth dose acquisitions and calibrations using a large diameter parallel-plate ionization chamber in a scanning water phantom (PTW, Freiburg, Germany; Models: Bragg Peak ionization chamber, MP3-P). Spot size and shape was measured using radiochromic film (Ashland Advanced Materials, Bridgewater NJ; Type: EBT3), and a synthetic diamond diode type scanned point by point in air (PTW Models: MicroDiamond, MP3-P). The measured data were used as inputs to generate a Monte Carlo-based model for a commercial radiotherapy planning system (TPS) (Varian Medical Systems, Inc., Palo Alto, CA; Model: Eclipse v13.7.15). The regular ProBeat-V system (sigma ~2.5mm) TPS model was available for comparison. A simulated base of skull case with small and medium targets proximal to brainstem was planned for both systems and compared. The spot sigma is determined to be 1.4mm at 221MeV at the isocenter and below 1mm at proximal distances. Integral depth doses were indistinguishable from the standard spot commissioning data. The TPS fit the spot profiles closely, giving a residual error maximum of 2.5% in the spot penumbra tails (below 5% of maximum) from the commissioned energies 69.4 to 221.3MeV. The resulting IMMPT plans were more conformal than the IMPT plans due to a sharper dose gradient (90-10%) 1.5mm smaller for the small target, and 1.3mm for the large target, at a representative central axial water equivalent depth of 7cm. We developed, implemented, and tested a new IMMPT system. The initial results look promising in cases where treatments can benefit from additional dose sparing to neighboring sensitive structures.

Comparison between diamond bur and diode laser to treat gingival hyperpigmentation

Gingival hyperpigmentation can be treated using a diamond bur or a diode laser. This research aimed to compare both techniques in terms of wound healing rates and pain experienced by patients. We used the split-mouth technique to treat gingival hyperpigmentation in 19 individuals. We recorded clinical parameters such as the degree of pain using Visual Analog Scale and the speed of healing using the PUSH (pressure, ulcer, scale, and healing) criteria. Our results showed that wound healing rate was faster and less pain was experienced by patients when a diode laser was used. We found that using a diode laser resulted in significantly less pain and faster healing rate than using a diamond bur for gingival depigmentation.

A 4.5 [formula omitted]m PIN diamond diode for detecting slow neutrons

The response of a PIN diamond diode with a 4.5 μm thick i-layer to α-particles from a 210Po radioactive source has been measured and compared to the response from a 300 μm thick single crystal type IIa diamond. The results show that this PIN diamond diode with thin i-layer can be employed to detect slow neutrons following absorption on a converter boron layer. Such a detector will operate at low voltages and be rather insensitive to gamma background and neutron radiation damage.

High power density nuclear battery prototype based on diamond Schottky diodes

We report here for the first time a fabrication of betavoltaic battery prototype consisting of 200 single conversion cells based on Schottky barrier diamond diodes which have been vertically stacked with ~24% 63Ni radioactive isotope. The maximum electrical output power of about 0.93 μW was obtained in total volume of 5 × 5 × 3.5 mm3. We used the ion-beam assisted lift-off technique to obtain conversion cells of minimal thickness comparable with the characteristic penetration length of beta-particles emitted by 63Ni isotope. The obtained value of 15 μm was limited by the mechanical strength of produced structures and process reliability. To check the performance of thin diamond based conversion cells we carried out IV-curves measurements at electron beam irradiation in SEM. We found that the sacrificial layer for the splitting of such thin conversion cell from HPHT diamond substrate did not cause a considerable degradation of device charge collection efficiency. As a result, the fabricated prototype provided the output power density of about 10 μW/cm3, that is the best known value for nuclear batteries based on 63Ni radioisotope. Moreover, the long half-life of 63Ni isotope gives the battery specific energy of about 3300 mWh/g that is an order of magnitude higher than the typical value of commercial chemical cells.