Diamond Solution-gated Field Effect Transistors Research Articles

Operation of Diamond Solution-Gated Field-Effect Transistor in the Frequency Domain

Here, the effect of frequency-domain sensing with diamond solution-gated field-effect transistors (SGFET) was investigated, where a sine wave with different frequencies (3, 30, 300, and 3 kHz) was applied at the gate. Variation of the power spectral density (PSD) amplitudes of the drain-source current was examined by using the NaCl gate electrolyte with various concentrations. With the increase of NaCl concentration, the PSD amplitudes basically increase for hydrogen-terminal diamond SGFET, however, the change of PSD amplitudes is not so obvious. When the diamond surface is partially oxidized by the UV radiation in the atmosphere, the PSD amplitudes increase first and then decrease with the concentration of NaCl aqueous solution. And the sensitivity of oxidized diamond SGFET is higher than that of hydrogen-terminated and increases with the increase of oxidation degree.

Gamma radiation effects on diamond field-effect biosensors with fibroblasts and extracellular matrix

Due to high biocompatibility, miniaturization, optical transparency and low production cost together with high radiation hardness the diamond-based sensors are considered promising for radiation medicine and biomedicine in general. Here we present detection of fibroblast cell culture properties by nanocrystalline diamond solution-gated field-effect transistors (SG-FET), including effects of gamma irradiation. We show that blank nanocrystalline diamond field-effect biosensors are stable at least up to 300 Gy of γ irradiation. On the other hand, gate current of the diamond SG-FET biosensors with fibroblastic cells increases exponentially over an order of magnitude with increasing radiation dose. Extracellular matrix (ECM) formation is also detected and analyzed by correlation of electronic sensor data with optical, atomic force, fluorescence, and scanning electron microscopies.

Threshold voltage control of electrolyte solution gate field-effect transistor by electrochemical oxidation

Diamond electrolyte solution-gate-field effect transistors (SGFETs) are suitable for applications as chemical ion sensors because of their wide potential window and good physical and chemical stabilities. In this study, we fabricated an anodically oxidized diamond SGFET from a full hydrogen-terminated diamond SGFET and demonstrated control of the device threshold voltage by irreversible anodic oxidation. The applied anodic bias voltage (VAO) was varied gradually from low to high (1.1–1.7 V). As the anodic oxidation proceeded, the threshold voltage shifted to more negative values with no degradation of hole mobility. Thus, anodic oxidation is a useful method for controlling the threshold voltage of diamond SGFETs.

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.

Real-time Monitoring of Cell Activities by Diamond Solution-gated Field Effect Transistors

In this study, we present basic aspects for real-time monitoring of cell growth of human cell lines. We successfully fabricated fully optically transparent diamond-based solution-gated field effect transistor (SG-FET) on glass substrates. The diamond transistor functionalities are demonstrated by the sensitivity of electrical characteristics to solutions with different Na+ and K+ ion concentrations, and pH. Moreover, the diamond SG-FETs exhibited sensitivities to the adhesion of proteins and cells, to the cell delamination, or even to the cell death.

Osteoblastic cells trigger gate currents on nanocrystalline diamond transistor

We show the influence of osteoblastic SAOS-2 cells on the transfer characteristics of nanocrystalline diamond solution-gated field-effect transistors (SGFET) prepared on glass substrates. Channels of these fully transparent SGFETs are realized by hydrogen termination of undoped diamond film. After cell cultivation, the transistors exhibit about 100× increased leakage currents (up to 10nA). During and after the cell delamination, the transistors return to original gate currents. We propose a mechanism where this triggering effect is attributed to ions released from adhered cells, which depends on the cell adhesion morphology, and could be used for cell culture monitoring.

Fundamentals and Applications of Diamond

Dear colleagues, We are pleased to introduce you to this Special Issue of physica status solidi (a), focussed on fundamental and applied science and technology of diamond and nanodiamond materials. This special issue aims at providing a brief but hopefully broad overview of those topics that are today at the centre of the diamond community's current interests, such as diamond growth and doping, colour centres, nanophotonics, devices and electronics, bioapplications of diamond and nanodiamonds, surface properties, etc. The Feature Article by Dean Ho and Han Man 1 reviews the use of diamond materials in various nanomedicine applications, with a particular focus on therapeutics and drug delivery. They demonstrate that, in addition to their well-known properties such as biocompatibility and outstanding imaging capability, diamond nanoparticles are promising vehicles for drug delivery resulting in enhanced therapeutic efficacy and reduced premature drug release. This exciting field of applications is expected to grow rapidly with the full understating and control over the surface functionality of diamond nanomaterials. A relatively recent field of excitement for the diamond community is nanophotonics, an area of research that has rapidly evolved from the study of colour centres in bulk diamond to a plethora of phenomena and applications enabled by a precise nanostructuring of diamond single crystals. In their Feature Article, Birgit Hausmann and colleagues 2 from Harvard University review some of their recent contributions, such as the use of diamond nanowires to increase single photo collection from nitrogen-vacancy (NV) centres embedded in these nanostructures, or the coupling of single NV centres to planar resonators on-chip. This article highlights the outstanding challenges that still need to be addressed both in terms of fabrication nanotechnology, implantation of colour centres, and device design. The third Feature Article in this special issue, by Markus Dankerl and colleagues 3 of the Walter Schottky Institute, reviews solution-gated field effect transistors (SGFETs) based on surface-conductive single crystalline diamond with a focus on bioelectronic applications, in particular for the development of cell-transistor electronic interfaces. The article covers technology aspects, fundamental issues of the diamond/electrolyte interface, and finally reports on the successful recording of cell's action potentials using arrays of diamond SGFETs. In a special issue related to diamond, the most demanding challenge for the community, i.e. the growth of high quality diamond films and their doping, cannot be missing. In the Editor's Choice article, André Sartori and co-workers 4 provide a detailed study of in-situ boron doping during heteroepitaxial growth of diamond, a promising path towards the preparation of doped, high-quality, large area diamond thin films, which is a step that seems mandatory for the success of any of the potential applications of diamond in electronics. In another contribution, Jocelyn Achard et al. 5 explore the suitability of boron-doped freestanding diamond single crystals for vertical power electronic devices. In contrast to the most standard co-planar structures, the vertical configuration offers several advantages, at the expense of requiring high quality, heavily doped, thick films. The electrical characterization of diamond films as well as of diamond devices is still a very active topic in the diamond community, and is well represented in this special issue of physica status solidi (a). For instance, the contribution by Yuto Hoshino and colleagues 6 reports on the electrical properties of a novel lateral p–n junction diode fabricated by selective growth of phosphorous n+ diamond, aiming at avoiding some of the drawbacks of vertical p–n junctions. Two studies report on fundamental aspects of the electronic properties of charge carriers in diamond films. J. Barjon et al. 7 characterize homoepitaxial boron-doped diamond, grown with a very residual donor impurity concentration which results in low compensation and thus films exhibiting high conductivities. In their contribution, P. Ščajev et al. 8, provide an extensive study on the effect of the crystalline structure of diamond films on the carrier recombination and diffusivity. With this special issue of physica status solidi (a) we do not only aim at providing you with a selection of the currently most active fields of research related to the science, technology, and applications of diamond. In addition, we also hope that the contributions included in this issue can help to point out the challenges ahead while at the same time provide inspiration for your future work. Garching & Hasselt, September 10, 2012 Jose A. Garrido Miloš Nesládek Ken Haenen

Low-frequency noise in diamond solution-gated field effect transistors

Electronic noise is investigated in diamond solution-gated field effect transistors. They exhibit 1/f-type noise, which is evaluated according to Hooge’s empirical relation. Correcting for the contribution of access regions, the Hooge parameter is found to be inversely proportional to the carrier density, suggesting that the noise originates from fluctuations in the number of charge carriers. Trapping and detrapping of charge carriers at dislocations of the diamond crystal is considered the main source of noise. An effective gate voltage noise of 16 μV rms is observed, which is comparable to the noise of similar devices based on Si and GaN.

Miniaturized diamond field-effect transistors for application in biosensors in electrolyte solution

The authors fabricated diamond solution-gate field-effect transistors (SGFETs) with miniaturization of the channel length to 5μm by photolithography. The channel surface was directly functionalized with amine by ultraviolet irradiation in an ammonia gas for 4h and aminated diamond SGFETs were sensitive to pH by 40mV∕pH. Urease was immobilized on the amine-modified channel surface, which was sensitive to urea by 27μA/decade from 10−5M to 10−2M. The authors fabricated submicron-sized (500nm) diamond SGFETs using electron-beam lithography. The transconductance (gm) was 56mS∕mm, which was 930-fold greater than that of the 500μm channel length.

Label-free DNA sensors using ultrasensitive diamond field-effect transistors in solution

Charge detection biosensors have recently become the focal point of biosensor research, especially field-effect-transistors (FETs) that combine compactness, low cost, high input, and low output impedances, to realize simple and stable in vivo diagnostic systems. However, critical evaluation of the possibility and limitations of charge detection of label-free DNA hybridization using silicon-based ion-sensitive FETs (ISFETs) has been introduced recently. The channel surface of these devices must be covered by relatively thick insulating layers ( SiO2, Si3N4, Al2O3, or Ta2O5) to protect against the invasion of ions from solution. These thick insulating layers are not suitable for charge detection of DNA and miniaturization, as the small capacitance of thick insulating layers restricts translation of the negative DNA charge from the electrolyte to the channel surface. To overcome these difficulties, thin-gate-insulator FET sensors should be developed. Here, we report diamond solution-gate FETs (SGFETs), where the DNA-immobilized channels are exposed directly to the electrolyte solution without gate insulator. These SGFETs operate stably within the large potential window of diamond (>3.0 V). Thus, the channel surface does not need to be covered by thick insulating layers, and DNA is immobilized directly through amine sites, which is a factor of 30 more sensitive than existing Si-ISFET DNA sensors. Diamond SGFETs can rapidly detect complementary, 3-mer mismatched (10 pM) and has a potential for the detection of single-base mismatched oligonucleotide DNA, without biological degradation by cyclically repeated hybridization and denature.

PH-sensitive diamond field-effect transistors (FETs) with directly aminated channel surface

We have introduced pH sensors fabricated on diamond thin films through modification of the surface-terminated atom. We directly modified the diamond surface from hydrogen to amine or oxygen with ultraviolet (UV) irradiation under ammonia gas. The quantified amine site based on the spectra obtained by X-ray photoelectron spectroscopy (XPS) is 26% (2.6 × 10 14 cm −2) with UV irradiation for 8 h and its coverage is dependent on the UV irradiation time. This directly aminated diamond surface is stable with long-term exposure in air and electrolyte solution. We fabricated diamond solution-gate field-effect transistors (SGFETs) without insulating layers on the channel surface. These diamond SGFETs with amine modified by direct amination are sensitive to pH (45 mV/pH) over a wide range from pH 2 to 12 and their sensitivity is dependent on the density of binding sites corresponding to UV irradiation time on the channel surface.