Over the past two decades, there has been an increasing trend towards miniaturization of both biological and chemical sensors and their integration with miniaturized sample pre-processing and analysis systems. These miniaturized lab-on-chip devices have several functional advantages including low cost, their ability to analyze smaller samples, faster analysis time, suitability for automation, and increased reliability and repeatability. Electrical based sensing methods that transduce biological or chemical signals into the electrical domain are a dominant part of the lab-on-chip devices. A vital part of any electrochemical sensing system is the reference electrode, which is a probe that is capable of measuring the potential on the solution side of an electrochemical interface. Research on miniaturization of this crucial component and analysis of the parameters that affect its performance, stability and lifetime, is sparse. In this paper, we present the basic electrochemistry and thermodynamics of these reference electrodes and illustrate the uses of reference electrodes in electrochemical and biological measurements. Different electrochemical systems that are used as reference electrodes will be presented, and an overview of some contemporary advances in electrode miniaturization and their performance will be provided.

The potential diagram for field-effect transistors used to detect charged biological macromolecules in an electrolyte is presented for the case where an insulating cover layer is used over a conventional eletrolyte-insulator metal-oxide-semiconductor (EIMOS) structure to tether or bind the biological molecules to a floating gate. The layer of macromolecules is modeled using the Poisson-Boltzmann equation for an ion-permeable membrane. Expressions are derived for the charges and potentials in the EIMOS and electrolyte-insulator-semiconductor structures, including the membrane and electrolyte. Exact solutions for the potentials and charges are calculated using numerical algorithms. Simple expressions for the response are presented for low solution potentials when the Donnan potential is approached in the bulk of the membrane. The implications of the model for the small-signal equivalent circuit and the noise analysis of these structures are discussed.

Field-effect sensors used to detect and identify biological species have been proposed as alternatives to other methods such as fluorescence deoxyribonucleic acid (DNA) microarrays. Sensors fabricated using commercial complementary metal-oxide-semiconductor technology would enable low-cost and highly integrated biological detection systems. In this paper, the small-signal and noise modeling of biosensors implemented with electrolyte-insulator-semiconductor structures is studied, with emphasis on design guidelines for low-noise performance. In doing so, a modified form of the general charge sheet metal-oxide-semiconductor field-effect transistor model that better fits the electrolyte-insulator-semiconductor structure is used. It is discussed how if the reference electrode and the insulator-electrolyte generate no noise associated with charge transport, then the main noise mechanisms are the resistive losses of the electrolyte and the low-frequency noise of the field-effect transistor. It is also found that for realistic sensor geometries and high electrolyte concentrations, the noise from the field-effect transistor (FET) dominates the thermal noise from the electrolyte resistance, and the optimal biasing point for the FET for minimum noise is found to be around moderate inversion.

GdSi x O y gate dielectric films were deposited on Si(001) substrates using ultra-high-vacuum electron-beam evaporation from pressed-powder targets. Transmission electron microscopy showed that the films were amorphous as deposited and remained amorphous when annealed to temperatures up to 900 °C. Capacitance–voltage measurements indicate an equivalent oxide thickness (EOT) of 13.4 Å for a film with composition GdSi0.56O2.59 determined by in situ x-ray photoelectron emission spectroscopy. After forming gas annealing at 500 °C the EOT was reduced to 11.0 Å, at a physical thickness of 45 Å. The same film has a low leakage current of approximately 5.7×10−3 A cm−2 at +1 V, a reduction of 8.7×104 compared to current density estimates of SiO2 films with the same specific capacitance.

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NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=12744313&lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=12744313&lang=fr READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions?Contact the NRC Publications Archive team at PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1063/1.1608488Applied Physics Letters, 83, 13, pp. 2638Letters, 83, 13, pp. -2640Letters, 83, 13, pp. , 2003 Interfacial growth in HfO x N y gate dielectrics deposited using †"C 2 H 5 … 2 N ‡ The interface growth by oxygen diffusion has been investigated for 5 nm thick HfO x N y gate-quality dielectric films deposited on Si͑100͒ by low-pressure pulsed metalorganic chemical vapor deposition. Analysis by x-ray photoelectron spectroscopy of the films deposited using the precursor tetrakis ͑diethylamido͒ hafnium with O 2 showed that the films contained 4 at. % nitrogen. This increased to 11 at. % N when NO was used as the oxidant. Significant growth of the interface layer was observed for films exposed to air at ambient temperature and lower rates of growth were observed for vacuum annealed films and those with the higher N content. For films annealed in O 2 at temperatures in the range 600-900°C, the activation energies of the interfacial growth were 0.36 and 0.25 eV for N concentrations of 11 and 4 at. %, respectively. The results were interpreted in terms of atomic oxygen formation in the bulk and reaction at the interface. The increase in N incorporation from 4 to 11 at. % increases the crystallization temperature from between 500 and 600°C to between 600 and 700°C. Hafnium oxide has proven to be one of the most promising candidates to replace SiO 2 as the gate insulator in sub-0.1-m complementary metal oxide semiconductor ͑CMOS͒ devices due to its relatively high dielectric constant and thermodynamic stability when in direct contact with Si.1,2 However, the high oxygen diffusion rate through hafnium oxide, 3 whic...

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Gadolinium oxide films were deposited on Si͑100͒ substrates from a rod-fed electron beam evaporator using a pressed-powder Gd 2 O 3 target. Films 25 nm thick were shown to be stoichiometric Gd 2 O 3 by Rutherford backscattering and had a dielectric constant at 100 kHz of 16.0 Ϯ 0.3. Transmission electron microscopy and X-ray reflectivity measurements showed that films 7-13 nm thick annealed in oxygen consisted of three distinct layers, an interfacial silicon dioxide layer next to the substrate, a second amorphous oxide layer containing silicon, gadolinium, and oxygen above this, and a polycrystalline Gd 2 O 3 layer on top. Annealing in oxygen reduced the leakage currents, increased the thickness of the silicon dioxide layer, and increased the grain size of the top Gd 2 O 3 layer. The characteristics of the leakage currents through the gadolinium oxide were consistent with a Frenkel-Poole conduction mechanism with a silicon-Gd 2 O 3 band offset of 1.8 V. Interfaces with excellent electrical properties, characteristic of good SiO 2 , were obtained after annealing in oxygen. Annealing of the films in vacuum prior to oxygen annealing reduced the thickness of the interfacial silicon dioxide.