Medical applications of diamond particles & surfaces

During diamond deposition on titanium substrates, two processes exist: (1) diffusion of hydrogen into a titanium substrate and the formation of hydride thereby degrading the mechanical properties of the substrate; and (2) competition among the rapid diffusion of carbon atoms into substrates, the formation of carbide and the nucleation of diamond crystals (thereby affecting the nucleation and growth rate of the diamond coating). To increase the diamond nucleation rate and prevent the rapid diffusion of hydrogen and carbon into the substrate, different surface treatments and interlayers were studied in this paper. Results showed that polishing with diamond pastes and ultrasonic pre-treatment in diamond suspensions will significantly increase the nuclei density of diamond crystals. However, the diffusion of hydrogen into the substrate could not be prevented. Pre-etching of the titanium substrate using hydrogen plasma for a short time significantly increased the nuclei density of diamond crystals. Results showed that on a TiN interlayer, there was no significant improvement in diamond nucleation and growth, and the deposited diamond coatings showed poor adhesion. New diamond crystals were formed on the DLC interlayer in which DLC acted as the precursor for diamond nucleation. However, the so-formed diamond coating showed spallation. The plasma nitrided layer could prevent the rapid diffusion of hydrogen and carbon into the titanium substrate, but results showed a relatively low nucleation density of diamond crystals and poor adhesion. A graded interlayer combining plasma nitriding followed by plasma carbonitriding was effective in preventing the rapid diffusion of hydrogen and carbon into the substrate and improving the nucleation rate and adhesion of diamond coating.

Effects of pre-treatments and interlayers on the nucleation and growth of diamond coatings on titanium substrates

Ferroelectric and piezoelectric responses of (110) and (001)-oriented epitaxial Pb(Zr0.52Ti0.48)O3 thin films on all-oxide layers buffered silicon

Integration of PbZr0.52Ti0.48O3 (PZT) films on glass substrates is of high importance for device applications. However, to make use of the superior ferro- and piezoelectric properties of PZT, well-oriented crystalline or epitaxial growth with control of the crystal orientation is a prerequisite. In this article, we report on epitaxial growth of PZT films with (100)- and (110)-orientation achieved by utilizing Ca2Nb3O10 (CNO) and Ti0.87O2 (TO) nanosheets as crystalline buffer layers. Fatigue measurements demonstrated stable ferroelectric properties of these films up to 5 × 109 cycles. (100)-oriented PZT films on CNO nanosheets show a large remnant polarization of 21 μC/cm2 that is the highest remnant polarization value compared to (110)-oriented and polycrystalline films reported in this work. A piezoelectric response of 98 pm/V is observed for (100)-oriented PZT film which is higher than the values reported in the literature on Si substrates.

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Nanosheet controlled epitaxial growth of PbZr0.52Ti0.48O3 thin films on glass substrates

Reliable DNA detection is of great importance for the development of the Lab-on-chip technology. The effort of the most recent projects on this field is to integrate all necessary operations, such as sample preparation (mixing, PCR amplification) together with the sensor user for DNA detection. Among the different ways to sense the DNA hybridization, fluorescence based detection has been favored by the market. However, fluorescence based approaches require that the DNA targets are labeled by means of chromophores. As an alternative label-free DNA detection method, capacitance detection was recently proposed by different authors. While this effect has been successfully demonstrated by several groups, the model used for data analysis is far too simple to describe the real behavior of a DNA sensor. The aim of the present paper is to propose a different electrochemical model to describe DNA capacitance detection.

Interface Layering Phenomena in Capacitance Detection of DNA with Biochips

Evaluation of buffer layers for hot filament chemical vapor deposition diamond films on silicon substrates

Ferroelectric lead-zirconate-titanate (PZT) thin films were deposited by the pulsed laser deposition technique on Pt-coated (100) Si substrates. This study was focused on the investigation of the PZT film growth on (100) Si substrate at varying deposition parameters and electrical characterization of the films including hysteresis loop and fatigue properties by RT66A Standardized Ferroelectric Test System. PZT deposited at higher temperature (575°C in 450 mTorr O2 partial pressure) showed the best crystalline structure. The remnant polarization and the retained polarization of the ferroelectric capacitors were 13 µC/cm2 and 20 µC/cm2, respectively. The crystallographic properties of the films were determined using the x-ray diffractometer method. The cross-sectional transmission electron microscope results showed very smooth interfaces among different layers of films.

Synthesis of the PZT films deposited on pt-coated (100) Si substrates for nonvolatile memory applications

Biosensors are a special class of chemical sensors that take advantage of the high selectivity and sensitivity of biologically active material. We are currently investigating the characteristics of various deposited electrode coatings (Au and Pt) on 10 MHz quartz crystals using the sputtering method. We are also investigating the effect of magnetic behavior (by intermixing Fe and Ni with electrodes) on the binding nature of antigen with the substrate. A change in mass occurs due to the binding of antigens and antibodies on the surface of the thin film coating. The frequency change as a result of a change in mass makes it possible to use these crystals as biological sensor devices. This paper describes the construction of antibody-based piezoelectric crystals capable of detecting mycobacterial antigens in diluted cultures of attenuated M. tuberculosis. The microstructural features of these crystals have been studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The crystallographic properties have been characterized using the X-ray diffraction (XRD) method. The long term objective of this research is to develop a rapid quantitative method of analysis for the diagnosis of tuberculosis (TB) and other infections caused by mycobacteria, using biosensor technology.

A. Mangiaracina

Papers

Evaluation of buffer layers for hot filament chemical vapor deposition diamond films on silicon substrates

Synthesis of the PZT films deposited on pt-coated (100) Si substrates for nonvolatile memory applications

Fabrication of Piezoelectric Sensors for Biomedical Applications