H-terminated Diamond Surface Research Articles

First-principles investigation of oxidized Si- and Ge-terminated diamond (100) surfaces.

Diamond is a semiconductor material with remarkable structural, thermal, and electronic properties that has garnered significant interest in the field of electronics. Although hydrogen (H) and oxygen (O) terminations are conventionally favored in transistor designs, alternative options, such as silicon (Si) and germanium (Ge), are being explored because of their resilience to harsh processing conditions during fabrication. Density-functional theory was used to examine the non-oxidized and oxidized group-IV (Si and Ge)-terminated diamond (100) surfaces. The (3 × 1) reconstructed surfaces feature an ether configuration and show relative stability compared with the bare surface. Hybrid-functional calculations of the electronic properties revealed reduced fundamental bandgaps (<1eV) and lower negative electron affinities (NEAs) than those of H-terminated diamond surfaces, which is attributed to the introduction of unoccupied Si (Ge) states and the depletion of negative charges. Furthermore, oxidation of these surfaces enhanced the stability of the diamond surfaces but resulted in two structural configurations: ether and ketone. Oxidized ether configurations displayed insulating properties with energy gaps of ∼4.3 ± 0.3eV, similar to H-terminated diamond (100) surfaces, whereas bridged ether configurations exhibited metallic properties. Oxidization of the metallic ketone configurations leads to the opening of relatively smaller gaps in the range of 1.1-1.7eV. Overall, oxidation induced a shift from NEAs to positive electron affinities, except for the reverse-ordered ketone surface with an NEA of -0.94eV, a value comparable to the H-terminated diamond (100) surfaces. In conclusion, oxidized group-IV-terminated diamond surfaces offer enhanced stability compared to H-terminated surfaces and display unique structural and electronic properties that are influenced by surface bonding.

Effect of sulfur and phosphorous doping on the growth rate of CVD diamond (111)

The purpose with the present study has been to theoretically investigate the effect of P (or S) doping on the chemical vapor deposition (CVD) growth rate of diamond. Density functional theory (DFT) calculations under periodic boundary conditions were then used for the investigation of the highly symmetric H-terminated diamond (111) surface. It was shown that both the thermodynamics and kinetics of P (or S) substitutional doping during diamond (111) growth were severely affected by the dopants (as compared with the non-doped situation).As a result of the thermodynamic calculations, except for P doping in C layer 1, the thermodynamic driving force for the diamond (111) growth was found to be largely improved by positioning P within the upper surface region of the H-terminated diamond (111) surface, while the opposite was true for S-doping. The P doping had a local vertical influence on the H abstraction energies, which was not the situation for the S doping. Also, both P and S doping showed a local lateral influence on the H abstraction energies, which was more pronounced for P doping.As a result of the kinetic calculations, the vertical and lateral P doping showed no local effect on the H abstraction energy barriers. In fact, these energy barriers became zero for P positioned in C layer 2 and downwards and were also zero for longer distances from the H adsorbate. On the other hand, the vertical S doping showed a local effect on the calculated barrier energies, but no lateral effect. The calculated energy barriers were zero for all surface H adsorbates on the H-terminated diamond (111) surface when S was positioned in the 4th atomic C layer. The different results for P doping versus S doping could be explained by the fact that S contains one electron extra and that P has a larger electronegativity value.Consequently, the results showed that P positioned in the upper diamond (111) surface lattice caused an enhancement in the diamond growth rate. The exception was the position in C atomic layer 1, for which both P doping and S doping had no effect on the diamond growth rate. On the other hand, a growth rate improvement was only found for S positioned in the 4th C layer. Due to the much higher (i.e., more positive) theoretical incorporation energies of S dopants versus P dopants in the diamond lattice, it has here been concluded that P doping is more effective than S doping in increasing the growth rate of the H-terminated diamond (111). Especially when considering that the H adsorbates are very mobile on this diamond surface, which has been shown by ab initio MD simulations at experimental CVD temperatures. These observations correlate well with experimental results.

Heteroatom Functionalization of H-Terminated Diamond Surfaces.

Diamond surface functionalization has received significant research interest recently. Specifically, H-termination has been widely adopted because it endows the diamond surface with negative electron affinity and the hole carrier is injected in the presence of surface transfer dopants. Exploring different functional groups' attachment on diamond surfaces and their impact on the electronic structure, using wet and dry chemical approaches, would hence be of interest in engineering diamond as a semiconductor. Here, we report the functionalization of the H-terminated diamond surface with nitrogen and sulfur heteroatoms. Surface characterization of functionalized diamond surfaces shows that these groups are well-distributed and covalently bonded to diamonds. Four chemical functional groups (-SH, -S-S-, -S-O, and -S=O) were found on the sulfurized diamond surface, and two groups (-NH2 and =NH) upon amination. We also report co-functionalization of surface with N and S (N-S), where sulfurization promotes sequential amination efficiency with reduced exposure time. Electrical measurement shows that heteroatom-modified diamond surfaces possess higher conductivity than H-terminated diamonds. Density functional theory (DFT) shows that upon functionalization with various N/S ratios, the conduction band minimum and valence band maximum downshift, which lowers the bandgap in comparison to an H-terminated diamond. These observations suggest the possibility of heteroatom functionalizations with enhanced surface electrical conductivity on the diamond that are useful for various electronic applications.

High performance ionic-liquid-gated air doped diamond field-effect transistors

We report successful fabrication of high performance ion-gated field-effect transistors (FETs) on hydrogenated diamond surface. Investigations on the hydrogen (H)-terminated diamond by Hall effect measurements shows Hall mobility as high as ∼200 cm2 V−1 s−1. In addition we demonstrate a rapid fabrication scheme for achieving stable high performance devices useful for determining optimal growth and fabrication conditions. We achieved H-termination using hydrogen plasma treatment with a sheet resistivity as low as ∼1.3 kΩ/sq. Conductivity through the FET channel is studied as a function of bias voltage on the liquid ion-gated electrode from −3.0 to 1.5 V. Stability of the H-terminated diamond surface was studied by varying the substrate temperature up to 350 °C. It was demonstrated that the sheet resistance and carrier densities remain stable over 3 weeks in ambient air atmosphere even at substrate temperatures up to 350 °C, whereas increasing temperature beyond this limit has effected hydrogenation. This study opens new avenues for carrying out fundamental research on diamond FET devices with ease of fabrication and high throughput.

First-principles study of formation and performance of diamond (111)/Al interface

The simple and convenient metallic mask method is a significant method of preparing diamond nanostructures. The metallic mask method has poor repeatability and can not give the ideal results, because it is supported by no theory about formation of surface mental nanoparticles and its technological parameters are optimized by no experimental techniques that are expensive either. Aiming at the formation and performance of the diamond/Al interface, this paper adopts the first-principles to study the adsorption and migration behavior of Al atoms on the H-terminated diamond surface and the structure of the diamond/Al interface. The results show that the highest adsorption energy is at the T4 position, which is only 0.181 eV, through comparing the adsorption energies of Al atoms at the highly symmetrical positions (Top, Br, H3 and T4) on the surface of the H-terminated diamond (111). The adsorption energies at these different positions are similar and the maximum difference is only 0.019 eV. There is formed no chemical bond, although Al has partial charge transfer on the H-terminated surface through the analysis of differential charge density and worse layout distribution. This phenomenon can be considered as electrostatic adsorption. That is to say, the adsorption of Al atoms are physical adsorption. The smooth potential energy surface also makes it easier for Al atoms to migrate on the diamond surface. The calculation results reveal that the migration activation energies of the two possible migration paths (from T4 position to Br position and from T4 to Top position) are 0.011 eV and 0.026 eV respectively. The above results imply that the metal Al and diamond are mainly connected by weak force, so the adhesion work of the three diamond/Al interface structures is compared based on the geometric stacking structure. The results show that the adhesion work of the three interfaces is around 0. These results indicate that the stability of the diamond/Al interface is not high and the stable structure of the interface is easily destroyed when the external environment changes. This speculation can be confirmed in molecular dynamics. When the simulated temperature is 300 ℃, the liquefied metal Al obviously accumulates into spheres. According to the above research results, we deduce that the metallic mask method does not require high requirements for the relationship between the metal and the substrate material, which depends mainly on the surface topography of the base material. This research provides an important theoretical reference for understanding the formation mechanism of metal nanomasks.

Surface transfer doping of diamond using solution-processed molybdenum trioxide

The surface of hydrogen-terminated diamond (H-terminated diamond) supports a p-type surface conductivity when interfaced with high electron-affinity surface acceptors through the surface transfer doping process. High electron-affinity transition metal oxides (TMOs), such as MoO3, have been regarded as superior candidates in surface transfer doping of diamond, holding great promise for enabling practical diamond electronic devices. In this work, a simple, solution-processed method is demonstrated to deposit a molybdenum trioxide (MoO3) layer on H-terminated diamond surface to achieve surface transfer doping of diamond. The surface of diamond following the deposition of solution-processed MoO3 (sp-MoO3) experienced significant reduction in sheet resistivity, corresponding to an increase in hole density, compared with the pristine air-doped diamond. This hole accumulation layer induced by sp-MoO3 is thermally stable up to 450 °C, and demonstrates metallic conductivity down to 250 mK with a strong spin-orbit interaction (SOI) in the induced two-dimensional (2D) surface conducting layer. Our study demonstrates that sp-MoO3 is comparable with thermally-evaporated MoO3 in doping performance but with great advantage as a simple, inexpensive and highly flexible fabrication method for developing diamond electronics.

Palladium forms Ohmic contact on hydrogen-terminated diamond down to 4 K

A hydrogen-terminated diamond (H-terminated diamond) surface supports a two-dimensional (2D) p-type surface conductivity when exposed to the atmosphere, as a result of the surface transfer doping process. The formation of reliable Ohmic contacts that persist to cryogenic temperature is essential for the exploration of quantum transport in the diamond 2D conducting channel. Herein, the contact properties of Pd on H-terminated diamond have been fully investigated down to 4 K using transmission line method measurements. Pd is shown to form an Ohmic contact on H-terminated diamond with linear I–V characteristics and low specific contact resistance in the range of (8.4 ± 1) ×10−4 Ω·cm2 to (1.3 ± 0.2) ×10−3 Ω·cm2 for the temperature range of 300 K–4 K. This is in stark contrast to reference devices with Au/Pt/Ti contacts, which exhibit a significant temperature dependence and non-Ohmic behavior at low temperature. Using 2D thermionic emission theory, a negative Schottky barrier height (SBH), − 23 ± 1 meV, between Pd and H-terminated diamond has been determined, in comparison to a positive SBH of 42 ± 1 meV for the Au/Pt/Ti/H-terminated diamond interface. These results show that Pd serves as an excellent candidate for forming reliable Ohmic contacts on H-terminated diamond for enabling precise electrical transport measurements at cryogenic temperature.

H-Terminated Diamond Surface Band Bending Characterization by Angle-Resolved XPS

Concerning diamond-based electronic devices, the H-terminated diamond surface is one of the most used terminations as it can be obtained directly by using H2 plasma, which also is a key step for diamond growth by chemical vapour deposition (CVD). The resultant surfaces present a p-type surface conductive layer with interest in power electronic applications. However, the mechanism for this behavior is still under discussion. Upward band bending due to surface transfer doping is the most accepted model, but has not been experimentally probed as of yet. Recently, a downward band bending very near the surface due to shallow acceptors has been proposed to coexist with surface transfer doping, explaining most of the observed phenomena. In this work, a new approach to the measurement of band bending by angle-resolved X-ray photoelectron spectroscopy (ARXPS) is proposed. Based on this new interpretation, a downward band bending of 0.67 eV extended over 0.5 nm was evidenced on a (100) H-terminated diamond surface.

Carrier mobility enhancement on the H-terminated diamond surface

The surface conductivity on the H-terminated diamond is still an interesting topic in the field of diamond electronics. Until now, the carrier mobility in the conductive channel has been limited to below 200cm2/Vs due to the various surface scattering mechanisms. In this paper, a high mobility conductive channel on the H-terminated diamond surface was reported. Firstly, the high quality diamond films were deposited on the commercial CVD diamond substrates. After polishing, the H-termination was obtained by hydrogen plasma treatment. The surface morphology of the H-terminated diamond was observed by atomic force microscope (AFM) and scanning electron microscope (SEM). The crystal quality on the diamond surface was characterized by Raman spectroscopy. The impurities in the crystals were tested by photoluminescence spectroscopy. The surface conductivity of H-terminated diamond was monitored comprehensively by Hall test. It can be found that the sheet resistance decreases much and the carrier mobility increases dramatically after the hydrogen plasma treatment and mechanical cleaning. The maximum mobility value is up to 365cm2/Vs with carrier density of 2.9 × 1012 cm−2, which is the highest value reported. Raman spectra of diamond surface show that a peak appears at 1121.4 cm−2 after the hydrogen plasma treatment, which corresponds to the nanocrystal diamond or carbon clusters of sp3 bonded material. The corresponding mobility enhancement mechanism on the H-terminated diamond surface was proposed.

Electrical property measurement of two-dimensional hole-gas layer on hydrogen-terminated diamond surface in vacuum-gap-gate structure

Hydrogen-terminated diamond metal-insulator-semiconductor field-effect transistors are candidates for power devices that require a high breakdown field and stable, high-frequency operation. A two-dimensional hole-gas layer can form on H-terminated diamond surfaces. To understand the electrical properties of bare H-terminated diamond surfaces, we investigate the surface impurities on a H-terminated diamond surface in a vacuum-gap gate structure, which uses a H-terminated diamond channel and a vacuum gap as gate dielectrics. To obtain a bare surface without surface adsorbate, the device is annealed in a vacuum. The transconductance is increased by removing adsorbates. The mobility and interface-state density at the H-terminated diamond surface with no adsorbates are 25 cm2 V−1 s−1 and 1 × 1012 cm−2 eV−1, respectively.

First principles calculations of the adsorption and migration behaviors of N atoms on the H-terminated diamond (0 0 1) surface

In this paper, the adsorption and migration behaviors of nitrogen (N) atoms on the hydrogen -terminated diamond (0 0 1) surface [H-Ter-D (0 0 1) surface] were investigated. The adsorption energy, the electron charge and the magnetic moment were calculated through first principles methods. The investigation results show that on the fully H-Ter-D (0 0 1) surface, all surface C atoms have saturated bonds. However, the N atom can abstract the H atom from a surface carbon atom nearby or lead to the bond breaking of the dimer carbon atoms to form bonds with the surface carbon atoms. The maximum energy of adsorption reaches to 3.47 eV, corresponding to a stable configuration structure. The charge analysis and the density of state analysis further reveal that the N atom adsorbed has unpaired electrons, which provides the opportunity for adsorption of CH radicals. On the H-Ter-D (0 0 1) surface with one open radical site (1ORS) slab, the N atom can abstract the H atom from a surface carbon atom nearby and bond with the dimer carbon atoms. The adsorption energy rises to 4.85 eV. On the H-Ter-D (0 0 1) surface with the 2ORS slab, the activation energy for a N atom to migrate along the dimer chain to the next dimer is 1.31 eV. Moreover, the adsorption of the N atom on the 1ORS surface promotes the adsorption of a C atom nearby and improves the ability of C atom migration, which is beneficial for the growth of the diamond grains. According to the charge transform analysis, the electronegativity of N atoms plays an important role in their adsorption behaviors. In addition, when the N atom has been adsorbed on the H-Ter-D (0 0 1) surface, it could still be abstracted by the other deposited N atoms; this phenomenon may be the reason for a low deposition efficiency of N atoms in the N-doped diamond films.

Chemical modification of diamond surface by a donor–acceptor organic chromophore (P1): Optimization of surface chemistry and electronic properties of diamond

The first systematic study of P1-dye attachment to the surface of H-terminated boron-doped diamond (BDD) surface was carried out. Details about surface anchoring chemistry were explored on model nanodiamond particles. The electronic properties of boron doped diamond films were tuned from semiconducting to quasi-metallic ones. The relevant materials were analyzed by advanced chemical analysis, zeta-potential, IR and TEM (nanoparticles), Raman, XPS, AFM, SEM, Hall-effect and by in-depth photo/electrochemical studies (films). An improved photochemical grafting protocol was developed leading to a factor of 3 enhancement in photocurrent on comparable diamond electrodes. The champion electrode provided at 1 sun illumination a photocurrent of 6.6μAcm−2 which is the best value ever reported for a flat BDD electrode.

Al2O3 dielectric layers on H-terminated diamond: Controlling surface conductivity

This study investigates how the surface conductivity of H-terminated diamond can be preserved and stabilized by using a dielectric layer with an in situ post-deposition treatment. Thin layers of Al2O3 were grown by plasma enhanced atomic layer deposition (PEALD) on H-terminated undoped diamond (100) surfaces. The changes of the hole accumulation layer were monitored by correlating the binding energy of the diamond C 1s core level with electrical measurements. The initial PEALD of 1 nm Al2O3 resulted in an increase of the C 1s core level binding energy consistent with a reduction of the surface hole accumulation and a reduction of the surface conductivity. A hydrogen plasma step restored the C 1s binding energy to the value of the conductive surface, and the resistance of the diamond surface was found to be within the range for surface transfer doping. Further, the PEALD growth did not appear to degrade the surface conductive layer according to the position of the C 1s core level and electrical measurements. This work provides insight into the approaches to establish and control the two-dimensional hole-accumulation layer of the H-terminated diamond and improve the stability and performance of H-terminated diamond electronic devices.

14.8-MeV Neutron Irradiation on H-Terminated Diamond-Based MESFETs

Field-effect transistors (FETs) fabricated on hydrogen-terminated diamond surface have been heavily irradiated with 14.8-MeV neutrons in order to evaluate their possible application in very high neutron fluence environments. The dc performance of the diamond-based FETs, such as drain saturation current and maximum transconductance, has been studied as a function of a 14.8-MeV neutron fluence up to $10^{14}$ n/cm2, delivered in five steps. The effects on electrical properties of H-terminated diamond surface have also been investigated during the neutron irradiation experiments. The Hall parameters, i.e., sheet hole concentration, hole mobility, and sheet resistance, were monitored before and after each irradiation. The performance remains stable during all the neutron fluence steps, thus assessing a remarkable radiation hardness of diamond-based devices. To the best of our knowledge, this is the first published data on 14-MeV neutron tolerance of diamond FET devices.

H-terminated diamond field effect transistor with ferroelectric gate insulator

An H-terminated diamond field-effect-transistor (FET) with a ferroelectric vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer gate insulator was fabricated. The VDF-TrFE film was deposited on the H-terminated diamond by the spin-coating method and low-temperature annealing was performed to suppress processing damage to the H-terminated diamond surface channel layer. The fabricated FET structure showed the typical properties of depletion-type p-channel FET and showed clear saturation of the drain current with a maximum value of 50 mA/mm. The drain current versus gate voltage curves of the proposed FET showed clockwise hysteresis loops due to the ferroelectricity of the VDF-TrFE gate insulator, and the memory window width was 19 V, when the gate voltage was swept from 20 to −20 V. The maximum on/off current ratio and the linear mobility were 108 and 398 cm2/V s, respectively. In addition, we modulated the drain current of the fabricated FET structure via the remnant polarization of the VDF-TrFE gate and obtained an on/off current ratio of 103 without applying a DC gate voltage.

Influence of non-adherent yeast cells on electrical characteristics of diamond-based field-effect transistors

Diamond thin films provide unique features as substrates for cell cultures and as bio-electronic sensors. Here we employ solution-gated field effect transistors (SGFET) based on nanocrystalline diamond thin films with H-terminated surface which exhibits the sub-surface p-type conductive channel. We study an influence of yeast cells (Saccharomyces cerevisiae) on electrical characteristics of the diamond SGFETs. Two different cell culture solutions (sucrose and yeast peptone dextrose–YPD) are used, with and without the cells. We have found that transfer characteristics of the SGFETs exhibit a negative shift of the gate voltage by −26mV and −42mV for sucrose and YPD with cells in comparison to blank solutions without the cells. This effect is attributed to a local pH change in close vicinity of the H-terminated diamond surface due to metabolic processes of the yeast cells. The pH sensitivity of the diamond-based SGFETs, the role of cell and protein adhesion on the gate surface and the role of negative surface charge of yeast cells on the SGFETs electrical characteristics are discussed as well.

Electronic Properties of Various B-Doped Diamond(111)// Dye Molecule Interfaces

Diamond is a widely known material for its many excellent properties (e.g., high thermal conductivity, high break down voltage, transparency, chemical intertness and bio-compatability). A B-doped diamond is an excellent p-type material for solar cell usage. Due to some specific properties (e.g., large chemical inertness, very high carrier mobility for both electron and holes, and high transparency), it is considered as one of the strongest candidates for photovoltic electric generation. However, in order to implement the usage of diamond in solar energy applications, properties like the i) electrochemical window, ii) possibility for interfacial charge transfer, and iii) stability of functionalized surface, have to be further studied and optimized. In the present investigation, the adsorption of different dye molecules onto H-terminated diamond (111) surfaces, have been theoretically studied using Density Functional Theory (DFT) calculations under periodic boundary conditions. The diamond surfaces were B-doped in order to make them p-type semi-conducting. The choice of dyes was based on the match between the electronic structures of these H-terminated B-doped diamond surfaces, and the respective dye molecules. The dye molecules in the present study included C20H13NO3S4 (A), C35H37NO2S3 (B), C34H38OS2(C), C32H36OS2(D), and C31H35S3Br(E). These dyes differ in the various functional groups, which have the role as electron acceptors. The main goal with the present study was thereby to investigate and compare the photovoltaic efficiency of the various dyes when attached to B-doped and H-terminated diamond (111) surfaces. Of a special interest was to study the i) absorption spectra of the dye, ii) degree of electron transfer over the diamond//dye interface, iii) electron transfer rate, iv) electron-hole recombination, and v) diamond//dye bond strength. The calculated absortion spectra for in principle all of the different dyes were shown to be located in the most intense part of the sunlight spectrum. For the E dye, the spectrum were more positioned towards the UV light range. The usage of a combination of these different dyes would, hence, be an optimal choice in order to improve the light harvesting in a photovoltaic process. Furthermore, the calculations identified the LUMO´s for the B, C, and D dyes to be positioned on the upper end of the molecules, which also will be the position of the electron acceptor when being excited by light. For the dyes A and E, there were though certain extentions of the LUMOs to the lower end of the molecules (i.e., towards the diamond surface), which will also increase the electron-hole recombination rates. Calculation of electron transfer was to ensure that the HOMO of these dyes were positioned at a lower energy compared to the upper edge of the valence band of the B-doped diamond surface. Moreover, all dyes were found to bind with strong C-C covalent bonds to the diamond (111) surface.

Efficiency and stability of spectral sensitization of boron-doped-diamond electrodes through covalent anchoring of a donor-acceptor organic chromophore (P1).

A novel procedure is developed for chemical modification of H-terminated B-doped diamond surfaces with a donor-π-bridge-acceptor molecule (P1). A cathodic photocurrent near 1 μA cm(-2) flows under 1 Sun (AM 1.5) illumination at the interface between the diamond electrode and aqueous electrolyte solution containing dimethylviologen (electron mediator). The efficiency of this new electrode outperforms that of the non-covalently modified diamond with the same dye. The found external quantum efficiency of the P1-sensitized diamond is not far from that of the flat titania electrode sensitized by a standard organometallic dye used in solar cells. However, the P1 dye, both pure and diamond-anchored, shows significant instability during illumination by solar light. The degradation is a two-stage process in which the initially photo-generated products further decompose in complicated dark reactions. These findings need to be taken into account for optimization of organic chromophores for solar cells in general.

A Theoretical Study of the Effect of Dopants on Diamond (100) Surface Stabilization for Different Termination Scenarios

The effect of dopants (N or B) on differently terminated diamond (100)-2 × 1 surfaces has in the present study been studied theoretically by using DFT (density functional theory) under periodic boundary conditions. The terminating species, X, include H, OH, Oontop, and Obridge. As a result of geometry optimization, the C–N and C–B bond lengths were calculated to be longer than for the situation with saturated binding conditions (i.e., the situation where N (or B) are binding to three other atoms, instead of four). Moreover, the X–Csurface-dopant angles were observed to decrease for the N-doped and increase for the B-doped senarios. In addition, the atomic charges and bond populations for the region surrounding the dopants were also carefully analyzed in order to compare the surface stabilization situations for non-, N- and B-doped diamond surfaces. For the H-terminated diamond surfaces, the C–H bonds became weakened when substituationally doped with either N or B. For the O-terminated diamond surfaces (i.e., both Oontop, and Obridge), the results showed opposite trends by strengthening (or weakening) the C–O bonds for the N- (or B-) doped system, respectivly. The adsorption energies for the various terminating species were observed to decrease when going from a nondoped to an N-doped situation and finally over to a B-doped situation. This is a result that strongly correlates with the calculated Csurface–X (X = H, OH, Oontop, Obridge) bond lengths. In addition, the effect of surface termination on the diamond surface stabilization energy, was observed to be in the following order: Obridge > Otop > H > OH. This result was valid for both non-, N- and B-doped diamond surfaces. The calculated spin density calculations indicated a local distribution of the unpaired electron in the N- and B-doped systems, respectively. This is a result that showed a strong correlation to the bond lengths surrounding the dopants and to the calculated adsorption energies for the terminating species, X. Moreover, the surface electronic structures (i.e., surface states) for the N- and B-doped systems were calculated and visualized by performing pDOS calculations. The results showed a shift of the Fermi levels for the N- and B-doped situations. As expected, the Fermi level was shifted toward the conduction band for the N-doped surfaces and toward the valence band for the B-doped systems. In addition, the pDOS spectra for the Oontop-termination showed extra states around the Fermi level, which were the result induced by the radical nature of this type of termination species.

Formation Mechanism of the H-terminated Diamond Surface

Formation Mechanism of the H-terminated Diamond Surface