Boron-doped Nanocrystalline Diamond Research Articles

Photochemical modification of a diamond surface using a pulsed UV laser as the energy source

The use of an excimer benchtop pulsed UV laser as the energy source for the photochemical modification of the surface of diamond films is reported. Boron-doped nanocrystalline diamond (NCD) films were deposited on Si wafers via plasma-enhanced chemical vapour deposition (PECVD). The as-deposited films were characterised by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Following characterisation, the surfaces of the films were subjected to a photochemical reaction with 2,2,2-trifluoroethyl undec-10-enoate using two different sources of radiation: a benchtop UV lamp (254 nm) and a KrF excimer pulsed UV laser (248 nm). The photochemically treated films were characterised by contact angle measurements and X-ray photoelectric spectroscopy (XPS) using non-treated films as a control. The use of a pulsed UV laser source was shown to reduce the photochemical reaction time from several hours to a few minutes.

Constructing a Hydrophilic Microsensor for High-Antifouling Neurotransmitter Dopamine Sensing.

Real-time sensing of dopamine is essential for understanding its physiological function and clarifying the pathophysiological mechanism of diseases caused by impaired dopamine systems. However, severe fouling from nonspecific protein adsorption, for a long time, limited conventional neural recording electrodes concerning recording stability. This study reported a high-antifouling nanocrystalline boron-doped diamond microsensor grown on a carbon fiber substrate. The antifouling properties of this diamond sensor were strongly related to the grain size (i.e., nanocrystalline and microcrystalline) and surface terminations (i.e., oxygen and hydrogen terminals). Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond microsensor exhibited enhanced antifouling characteristics against protein adsorption, which was attributed to the formation of a strong hydration layer as a physical and energetic barrier that prevents protein adsorption on the surface. This finally allowed for in vivo monitoring of dopamine in rat brains upon potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors. Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond (O-NCBDD) microsensor exhibited ultrahydrophilic properties with a contact angle of 4.9°, which was prone to forming a strong hydration layer as a physical and energetic barrier to withstand the adsorption of proteins. The proposed O-NCBDD microsensor exhibited a high detection sensitivity of 5.14 μA μM-1 cm-2 and a low detection limit of 25.7 nM. This finally allowed for in vivo monitoring of dopamine with an average concentration of 1.3 μM in rat brains upon 2 μL of potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors.

Surface morphology-assisted electrochemical conversion of carbon dioxide to formic acid via nanocrystalline boron-doped diamond electrodes

Due to its unmatched corrosion stability and overall versatility, boron-doped diamond (BDD) has superb potential as an electrode material for the production of valuable chemicals via electrochemical reduction of carbon dioxide (CO2). To advance its practical application, it is necessary to explore ways to achieve cost-effective fabrication of BDD electrodes, which can enable significant selectivity for product formation during CO2 electroreduction. Here, BDD electrodes of nanocrystalline form were fabricated employing two distinct chemical vapor deposition (CVD) techniques, which allow for substantial upscaling of electrode dimensions to match industrial/wafer-size standards. Thin (<400 nm) nanocrystalline BDD layers were fabricated at various synthesis temperatures to investigate its effect on the electrical, structural, and electrochemical characteristics. Furthermore, modification of the BDD layer crystallinity and morphology has been performed to significantly alter the overall electrode structure and sp3/sp2-carbon phase-composition. Finally, when employed as cathodes in electrochemical CO2 reduction, nanocrystalline BDD electrodes of modified structure demonstrated enhanced values of faradaic efficiency (FE) towards production of formic acid (HCOOH), surpassing FEHCOOH values observed for microcrystalline form of BDD cathodes. Reported findings present a basis for further development of BDD cathodes, including their design, structure, and composition, which leverages the advantages of scalable and cost-effective synthesis of BDD electrodes.

Comparative determination of atomic boron and carrier concentration in highly boron doped nano-crystalline diamond

Comparative determination of atomic boron and carrier concentration in highly boron doped nano-crystalline diamond

Superconducting boron doped nanocrystalline diamond microwave coplanar resonator

A coplanar waveguide resonator (CPR) is presented for kinetic inductance (Lk) and penetration depth (λL) measurements of superconducting boron doped nanocrystalline diamond (B-NCD) at microwave frequencies of 0.4 to 1.2 GHz and at temperatures below 3 K. Using finite element modelling and experimental measurements, this work demonstrates that thin granular B-NCD films (thickness d≈ 500nm) on Si have a large penetration depth (λL≈3.8μm), and therefore an associated high kinetic inductance per square (Lk,□≈ 670 to 690 pH/□). These values are much larger than those typically obtained for films on single crystal diamond, which is likely due to the high granularity of the nanocrystalline films. Based on the measured Q factors of the structure, the calculated surface resistance is found to be around ≈ 1 to 6μΩ at T<2 K in the 0.4 to 1.2 GHz range, demonstrating the potential for granular B-NCD for high quality factor superconducting microwave resonators and highly sensitive kinetic inductance detectors.

Microstructure and Anisotropic Order Parameter of Boron-Doped Nanocrystalline Diamond Films

Unconventional superconductivity in heavily boron-doped nanocrystalline diamond films (HBDDF) produced a significant amount of interest. However, the exact pairing mechanism has not been understood due to a lack of understanding of crystal symmetry, which is broken at the grain boundaries. The superconducting order parameter (Δ) of HBDDF is believed to be anisotropic since boron atoms form a complex structure with carbon and introduce spin-orbit coupling to the diamond system. From ultra-high resolution transmission electron microscopy, the internal symmetry of the grain boundary structure of HBDDF is revealed, which can explain these films’ unconventional superconducting transport features. Here, we show the signature of the anisotropic Δ in HBDDF by breaking the structural symmetry in a layered microstructure, enabling a Rashba-type spin-orbit coupling. The superlattice-like structure in diamond describes a modulation that explains strong insulator peak features observed in temperature-dependent resistance, a transition of the magnetic field-dependent resistance, and their oscillatory, as well as angle-dependent, features. Overall, the interface states of the diamond films can be explained by the well-known Shockley model describing the layers connected by vortex-like structures, hence forming a topologically protected system.

Ultrasensitive Diamond Microelectrode Application in the Detection of Ca2+ Transport by AnnexinA5-Containing Nanostructured Liposomes.

This report describes the innovative application of high sensitivity Boron-doped nanocrystalline diamond microelectrodes for tracking small changes in Ca2+ concentration due to binding to Annexin-A5 inserted into the lipid bilayer of liposomes (proteoliposomes), which could not be assessed using common Ca2+ selective electrodes. Dispensing proteoliposomes to an electrolyte containing 1 mM Ca2+ resulted in a potential jump that decreased with time, reaching the baseline level after ~300 s, suggesting that Ca2+ ions were incorporated into the vesicle compartment and were no longer detected by the microelectrode. This behavior was not observed when liposomes (vesicles without AnxA5) were dispensed in the presence of Ca2+. The ion transport appears Ca2+-selective, since dispensing proteoliposomes in the presence of Mg2+ did not result in potential drop. The experimental conditions were adjusted to ensure an excess of Ca2+, thus confirming that the potential reduction was not only due to the binding of Ca2+ to AnxA5 but to the transfer of ions to the lumen of the proteoliposomes. Ca2+ uptake stopped immediately after the addition of EDTA. Therefore, our data provide evidence of selective Ca2+ transport into the proteoliposomes and support the possible function of AnxA5 as a hydrophilic pore once incorporated into lipid membrane, mediating the mineralization initiation process occurring in matrix vesicles.

The effect of boron concentration on the electrical, morphological and optical properties of boron-doped nanocrystalline diamond sheets: Tuning the diamond-on-graphene vertical junction

In this paper, the effect of boron doping on the electrical, morphological and structural properties of free-standing nanocrystalline diamond sheets (thickness ~ 1 μm) was investigated. For this purpose, we used diamond films delaminated from a mirror-polished tantalum substrate following a microwave plasma-assisted chemical vapor deposition process, each grown with a different [B]/[C] ratio (up to 20,000 ppm) in the gas phase. The developed boron-doped diamond (BDD) films are a promising semiconducting material for sensing and high-power electronic devices due to band gap engineering and thermal management feasibility. The increased boron concentration in the gas phase induces a decrease in the average grain size, consequently resulting in lower surface roughness. The BDD sheets grown with [B]/[C] of 20,000 ppm reveal the metallic conductivity while the lower doped samples show p-type semiconductor character. The charge transport at room temperature is dominated by the thermally activated nearest-neighbor hopping between boron acceptors through impurity band conduction. At low temperatures (<300 K), the Arrhenius plot shows a non-linear temperature dependence of the logarithmic conductance pointing towards a crossover towards variable range hopping. The activation energy at high temperatures obtained for lowly-doped sheets is smaller than for nanocrystalline diamond bonded to silicon, while for highly-doped material it is similar. Developed sheets were utilized to fabricate two types of diamond-on-graphene heterojunctions, where boron doping is the key factor for tuning the shape of the current-voltage characteristics. The graphene heterojunction with the low boron concentration diamond sheet resembles a Schottky junction behavior, while an almost Ohmic contact response is recorded with the highly doped BDD sheet of metallic conductivity. The free-standing diamond sheets allow for integration with temperature-sensitive interfaces (i.e. 2D materials or polymers) and pave the way towards flexible electronics devices.

Conductive printable electrodes tuned by boron-doped nanodiamond foil additives for nitroexplosive detection

An efficient additive manufacturing-based composite material fabrication for electrochemical applications is reported. The composite is composed of commercially available graphene-doped polylactide acid (G-PLA) 3D printouts and surface-functionalized with nanocrystalline boron-doped diamond foil (NDF) additives. The NDFs were synthesized on a tantalum substrate and transferred to the 3D-printout surface at 200 °C. No other electrode activation treatment was necessary. Different configurations of low- and heavy-boron doping NDFs were evaluated. The electrode kinetics was analyzed using electrochemical procedures: cyclic voltammetry and electrochemical impedance spectroscopy. The quasi-reversible electrochemical process was reported in each studied case. The studies allowed confirmation of the CV peak-to-peak separation of 63 mV and remarkably high heterogeneous electron transfer rate constant reaching 6.1 × 10−2 cm s−1 for 10 k ppm [B]/[C] thin NDF fitted topside at the G-PLA electrode. Differential pulse voltammetry was used for effective 2,4,6-trinitrotoluene (TNT) detection at the studied electrodes with a 87 ppb limit of detection, and wide linearity range between peak current density and the analyte concentration (0.064 to 64 ppm of TNT). The reported electrode kinetic differences originate primarily from the boron-dopant concentration in the diamond and the various contents of the non-diamond carbon phase.Graphical abstract

Aluminium nitride thin films directly grown on conducting boron-doped nanocrystalline diamond films without using buffer layer for high frequency applications

Aluminium Nitride (AlN)-diamond hetero-structures are promising candidates for high frequency acoustic wave resonator applications. This paper reports the electrical, piezoelectric and mechanical properties of AlN films directly grown on boron-doped nanocrystalline diamond (B-NCD) films. X-ray diffraction (XRD) and Raman spectroscopy were used to determine the crystallinity of B-NCD and AlN films. The resistivity (∼8 ×107Ω.m) and dielectric constant (∼14) were obtained from the electrical characterisation of the fabricated Al/AlN/B-NCD capacitors. Piezoelectric coefficient (d33, 4.3 pmV−1) of AlN films was measured by piezo force microscopy (PFM) technique. Nanoindentation technique was used to determine the hardness (∼14 GPa) and elastic modulus (∼202 GPa) of AlN films. These different properties of AlN/B-NCD/Si (100) hetero-structure show that it will provide a high-performance platform to realize high frequency resonators for 5G applications.

Fabrication of a boron-doped nanocrystalline diamond grown on an WC-Co electrode for degradation of phenol.

Cemented carbide (WC–Co) is applied as the substrate instead of conventional ones such as Si, Ti, and Nb, on which nanocrystalline BDD films are deposited by hot filament chemical vapor deposition. Then the WC–Co/BDD electrodes are investigated by Field Emission Scanning Electron Microscopy (FE-SEM), Micro-Raman Spectroscopy, X-ray photoelectron spectroscopy (XPS), a four-point probe method, accelerated life test (ALT), and electrochemical analysis. According to the results, the BDD films deposited on the WC–Co substrate are highly uniform and pinhole-free with a grain size of 100 nm and a low compressive stress. The WC–Co/BDD electrode has a wide potential window of 3.8 V and low background currents in 0.5 mol L−1 H2SO4 electrolytes and shows a quasi-reversible behavior in the K3[Fe(CN)6] redox system. The electrode has a service life of more than 400 h in the ALT with 3 mol L−1 H2SO4 electrolytes at a constant current density of 1 A cm−2. These electrochemical performances of BDD films on the WC–Co substrate is similar to or even slightly better than that on the commonly used substrates. Finally, phenol is used as a pollutant to test the activity of the WC–Co/BDD electrode. The results of replicated experiments show that the average COD reduces from the initial 5795 to 85 mg L−1, and the average current efficiency is about 46%. This suggests that the WC–Co/BDD electrode has a good mineralization capacity in phenol with a high concentration.

Nitrogen-Incorporated Boron-Doped Nanocrystalline Diamond Nanowires for Microplasma Illumination.

The origin of nitrogen-incorporated boron-doped nanocrystalline diamond (NB-NCD) nanowires as a function of substrate temperature (Ts) in H2/CH4/B2H6/N2 reactant gases is systematically addressed. Because of Ts, there is a drastic modification in the dimensional structure and microstructure and hence in the several properties of the NB-NCD films. The NB-NCD films grown at low Ts (400 °C) contain faceted diamond grains. The morphology changes to nanosized diamond grains for NB-NCD films grown at 550 °C (or 700 °C). Interestingly, the NB-NCD films grown at 850 °C possess one-dimensional nanowire-like morphological grains. These nanowire-like NB-NCD films possess the co-existence of the sp3-diamond phase and the sp2-graphitic phase, where diamond nanowires are surrounded by sp2-graphitic phases at grain boundaries. The optical emission spectroscopy studies stated that the CN, BH, and C2 species in the plasma are the main factors for the origin of nanowire-like conducting diamond grains and the materialization of graphitic phases at the grain boundaries. Moreover, conductive atomic force microscopy studies reveal that the NB-NCD films grown at 850 °C show a large number of emission sites from the grains and the grain boundaries. While boron doping improved the electrical conductivity of the NCD grains, the nitrogen incorporation eased the generation of graphitic phases at the grain boundaries that afford conducting channels for the electrons, thus achieving a high electrical conductivity for the NB-NCD films grown at 850 °C. The microplasma devices using these nanowire-like NB-NCD films as cathodes display superior plasma illumination properties with a threshold field of 3300 V/μm and plasma current density of 1.04 mA/cm2 with a supplied voltage of 520 V and a lifetime stability of 520 min. The outstanding plasma illumination characteristics of these conducting nanowire-like NB-NCD films make them appropriate as cathodes and pave the way for the utilization of these materials in various microplasma device applications.

Fluctuation spectroscopy in granular superconductors with application to boron-doped nanocrystalline diamond

We perform a detailed calculation of the various contributions to the fluctuation conductivity of a granular metal close to its superconducting transition. We find three distinct regions of power law behavior in reduced temperature, $\eta=(T-T_c)/T_c$, with crossovers at $\Gamma/T_c$ and $E_{Th}/T_c$, where $\Gamma$ is the electron tunneling rate, and $E_{Th}$ is the Thouless energy of a grain. The calculation includes both intergrain and intragrain degrees of freedom. This complete theory of the fluctuation region in granular superconductors is then compared to experimental results from boron-doped nanocrystalline diamond, using the assumption of a constant phase breaking rate, $\tau_{\phi}^{-1}$. We find a semi-quantitative agreement between the theoretical and experimental results only in the case of large phase breaking. We argue that there may be a novel phase breaking mechanism in granular metals worthy of further experimental and theoretical investigation.

Contact resistance of various metallisation schemes to superconducting boron doped diamond between 1.9 and 300 K

Diamond is a material that offers potential in numerous device applications. In particular, highly boron doped diamond is attractive due to its superconductivity and high Young’s Modulus. The fabrication of stable, low resistance, ohmic contacts is essential to ensure proper device function. Previous work has established the efficacy of several methods of forming suitable contacts to diamond at room temperature and above, including carbide forming and carbon soluble metallisation schemes. Herein, the stability of several contact schemes (Ti, Cr, Mo, Ta and Pd) to highly boron doped nanocrystalline diamond was verified down to the cryogenic temperatures with modified Transmission Line Model (TLM) measurements. While all contact schemes remained ohmic, a significant temperature dependency is noted at Tc and at the lowest temperatures the contact resistances ranged from Ti/Pt/Au with (8.83 ± 0.10) × 10−4 Ω cm to Ta/Pt/Au with (8.07 ± 0.62) × 10−6 Ω cm.

Phase slips and metastability in granular boron-doped nanocrystalline diamond microbridges

A phase slip is a localized disturbance in the coherence of a superconductor allowing an abrupt 2π phase shift. Phase slips are a ubiquitous feature of one-dimensional superconductors and also have an analogue in two-dimensions. Here we present electrical transport measurements on boron-doped nanocrystalline diamond (BNCD) microbridges where, despite their three-dimensional macroscopic geometry, we find clear evidence of phase slippage in both the resistance-temperature and voltage-current characteristics. We attribute this behavior to the unusual microstructure of BNCD. We argue that the columnar crystal structure of BNCD forms an intrinsic Josephson junction array that supports a line of phase slippage across the microbridge. The voltage-state in these bridges is metastable and we demonstrate the ability to switch deterministically between different superconducting states by applying electromagnetic noise pulses. This metastability is remarkably similar to that observed in δ-MoN nanowires, but with a vastly greater response voltage.

Synthesis and Characterization of Nanocrystalline Boron-Doped Diamond Electrodes: Towards Electrochemical Reduction of CO2

The continuous increase of atmospheric carbon dioxide (CO2) concentration along with pollution of waters by organic wastes have led the scientific community to investigate novel strategies to address these worldwide environmental problem. Electrochemical methods are a promising approach to convert CO2 into a variety of useful chemicals and to remove contaminants from wastewater [1,2]. Nevertheless, it is necessary to develop inexpensive and chemically robust electrodes with long life-time in harsh electrochemical conditions for these processes to be efficient and economically viable.Boron-doped diamond (BDD) has been recently shown to be a promising material for electrochemical reduction of CO2 into formic acid and formaldehyde [3]. In contrast to thick microcrystalline BDD films, thin nanocrystalline BDD layers (thickness of 100 - 500 nm) provide a higher degree of flexibility in material properties, e.g. due to a variable diamond/non-diamond content, and allows efficient bottom-up nanostructuring, e.g. BDD growth on porous templates [4].In this work, we investigate nanocrystalline boron-doped diamond and composite BDD/SiC electrodes synthesized via microwave plasma enhanced chemical vapor deposition (MW PE CVD) method at different deposition temperatures (250 - 750°C) towards electrochemical reduction of CO2 in water-based electrolytes [5]. Fabricated electrodes were characterized by a variety of techniques, including Raman spectroscopy, scanning electron microscopy imaging and electrical conductivity measurements. Electrochemical properties of nanocrystalline BDD electrodes of various thickness, boron content and electrical conductivity were studied.This work has been supported by the Grant Agency of the Czech Republic (GACR) contract 19-09784Y.[1] I. Sirés et al., Environ Sci Pollut Res (2014) 21: 8336.[2] A. Goeppert et al., Chem. Soc. Rev. (2014), 43, 7995-8048.[3] K. Nakata et al., Angew. Chem. Int. Ed. (2014), 53, 871 –874.[4] V Petrák et al., Carbon (2017), 114, 457.[5] A. Taylor et al., J. Alloys. Compd., (2019) 800, 327-333

Effects of Rashba-spin–orbit coupling on superconducting boron-doped nanocrystalline diamond films: evidence of interfacial triplet superconductivity

Among the many remarkable properties of diamond, the ability to superconduct when heavily doped with boron has attracted much interest in the carbon community. When considering the nanocrystalline boron doped system, the reduced dimensionality and confinement effects have led to several intriguing observations most notably, signatures of a mixed superconducting phase. Here we present ultra-high-resolution transmission electron microscopy imaging of the grain boundary and demonstrate how the complex microstructure leads to enhanced carrier correlations. We observe hallmark features of spin–orbit coupling (SOC) manifested as the weak anti-localization effect. The enhanced SOC is believed to result from a combination of inversion symmetry breaking at the grain boundary interfaces along with antisymmetric confinement potential between grains, inducing a Rashba-type SOC. From a pronounced zero bias peak in the differential conductance, we demonstrate signatures of a triplet component believed to result from spin mixing caused by tunneling of singlet Cooper pairs through such Rashba-SOC grain boundary junctions.

Effect of Surface Oxygen on the Wettability and Electrochemical Properties of Boron-Doped Nanocrystalline Diamond Electrodes in Room-Temperature Ionic Liquids.

This paper reports on how the surface chemistry of boron-doped nanocrystalline diamond (BDD) thin-film electrodes (H vs O) affects the wettability and electrochemical properties in two room-temperature ionic liquids (RTILs): [BMIM][PF6] and [HMIM][PF6]. Comparative measurements were made in 0.5 mol L-1 H2SO4. The BDD electrodes were modified by microwave or radio-frequency (RF) plasma treatment in H2 (H-BDD), Ar (Ar-BDD), or O2 (O-BDD). These modifications produced low-, medium-, and high-oxygen surface coverages. Atomic O/C ratios, as determined by X-ray photoelectron spectroscopy (XPS), were 0.01 for H-BDD, 0.08 for Ar-BDD, and 0.17 for O-BDD. The static contact angle of ultrapure water on the modified electrodes decreased from 110° (H-BDD) to 41° (O-BDD) with increasing surface oxygen coverage, as expected as the surface becomes more hydrophilic. Interestingly, the opposite trend was seen for both RTILs as the contact angle increased from 20° (H-BDD) to 50° (O-BDD) with increasing surface oxygen coverage. The cyclic voltammetric background current and potential-dependent capacitance in both RTILs were largest for BDD electrodes with the lowest O/C ratio (H-BDD) and smallest contact angle. Slightly larger voltammetric background currents and capacitance were observed in [HMIM][PF6] than in [BMIM][PF6]. Capacitance values ranged from 8 to 16 μF cm-2 over the potential range for H-BDD and from 4 to 6 μF cm-2 for O-BDD. The opposite trend was observed in H2SO4 as the voltammetric background current and capacitance were largest for BDD electrodes with the highest O/C ratio (O-BDD) and smallest contact angle. In summary, reducing the surface oxygen on BDD electrodes increases the wettability to two RTILs and this increases the voltammetric background current and capacitance.

Low temperature synthesis of transparent conductive boron doped diamond films for optoelectronic applications: Role of hydrogen on the electrical properties

Transparent conductive electrodes are principal components in various optoelectronic devices and technologies. As such, diamond coatings in the form of electrically conductive thin films are envisioned to provide advantageous chemical and mechanical characteristics/stability in a variety of modern technologies including optoelectronics, biosensing, electrochemical and micromechanical systems. However, deposition of electrically conductive polycrystalline diamond coatings for such applications is currently a challenging task, since temperatures above 600 °C are usually required to ensure good diamond layer quality, which in turn limits the selection of substrates, to materials capable of withstanding exposure to high temperatures. In the present work, we investigate routes toward enhancement of electrical characteristics of nanocrystalline boron-doped diamond (BDD) films fabricated at low temperatures via chemical vapour deposition. We found that post-growth processing of BDD layers enhances their electrical properties, which otherwise are dependent on the employed deposition temperature regime. Finally, we show that integration of an electrically conductive Ti grid opens a route for fabrication of highly transparent and conductive composite nanocrystalline BDD electrodes over large areas at temperatures as low as 250 °C.

Photogenerated charge collection on diamond electrodes with covalently linked chromophore monolayers

Encouraged by its rich surface chemistry and excellent electrochemical properties, boron-doped nanocrystalline diamond (B:NCD) is a promising p-type photoelectrode in dye-sensitized solar cells. One method of diamond surface functionalization using stable carbon-carbon bonds involves the electrochemical grafting of diazonium salts. However, this method typically leads to multilayers that may complicate the transport of photogenerated charges. Here, we establish functionalization of B:NCD electrodes by a monolayer of ethynylphenyl molecules using sterically hindered 4-(trimethylsilyl)ethynylbenzenediazonium tetrafluoroborate. Both the density and structural orientation of the grafted layer are investigated by angular resolved X-ray photoelectron spectroscopy, confirming the presence of covalently grafted monolayers. After removal of the trimethylsilyl protective groups, the resulting ethynyl functionalities are employed to immobilize organic donor-acceptor chromophores via Sonogashira cross-coupling reactions. Homogenous surface coverage is achieved even on the B:NCD electrode. Atomic scale DFT computing reveals that for the chromophore with the strongest acceptor unit, efficient charge separation of 20 Å is obtained where photogenerated holes move directly into diamond. Yet, photocurrent and photovoltage measurements suggest competitive electron recombination to the diamond electrode via the redox electrolyte. Correlation between the density of the molecular layer and photocurrents/photovoltage provides better understanding of the charge generation and recombination pathways in diamond-organic photoelectrochemical cells.