“…The most common fabrication procedure of inlaid microdisk electrodes involves encapsulating carbon fibers or metal wires in glass capillaries and then polishing the tips to expose the microdisk surfaces. , Other methods have also been employed to produce an insulating sheath around the electrode material and include dip-coating metallic wires or carbon fibers with insulating polymers, ,, deposition of silica thin films, , and electrophoretic deposition of paint. − With the latter construction methods, insulating shields with thickness (b − a) comparable to the electrode radius a are usually produced (Figure A). The current interest for such kinds of electrodes, other than for small-volume and microenvironment applications, , is largely driven by the use of microelectrodes as tips in scanning electrochemical microscopy (SECM). , In this technique, the parameter b/a , usually defined as RG, has strong influence on the Faradaic tip current, especially when the tip is moved in the vicinity of an inert substrate. , 1 Schematic representation of (A) electrode dimensions and simulation domain and (B) diffusion at a TSMs.…”
The cyclic voltammetric behavior of disk microelectrodes surrounded by thin insulating shields (TSM) was investigated from both theoretical and experimental points of view. In particular, microdisks with shields of thickness (b - a), a few electrode radii (a) were considered. A finite difference simulation procedure with a nonuniform, expanding spatial grid, already available in the literature, was employed for predicting shape and height of the voltammograms. The parameters of this numerical simulation were optimized again, and the steady-state limiting currents found in this work for a range of TSMs compared well with previous publications. The steady-state limiting current at TSMs was enhanced with respect to microelectrodes surrounded by thick insulating sheaths (i.e., b >> a), and steady-state conditions were achieved faster. Under these conditions, the difference in potential observed on the forward and backward waves, when the current is half of its maximum value (deltaE(1/2)), was almost equal to zero. Nonsteady-state cyclic voltammograms were also simulated using the optimized parameters, and the effect of scan rate on deltaE(1/2) was examined in detail. Based on this dependence, a voltammetric procedure for the simultaneous determination of microdisk radius and its insulator thickness was proposed. Experimental measurements were performed by using platinum wires, 10-12.5-microm radius, and carbon fibers, 4-microm radius, coated with 4-6-microm-thick electrophoretic paint. The shield thickness produced around the wires was such that b/a < 3. The experimental results obtained were in general congruent with the theory and demonstrated the validity of the method proposed here for the simultaneous determination of radius and shield thickness of a TSM.
“…The most common fabrication procedure of inlaid microdisk electrodes involves encapsulating carbon fibers or metal wires in glass capillaries and then polishing the tips to expose the microdisk surfaces. , Other methods have also been employed to produce an insulating sheath around the electrode material and include dip-coating metallic wires or carbon fibers with insulating polymers, ,, deposition of silica thin films, , and electrophoretic deposition of paint. − With the latter construction methods, insulating shields with thickness (b − a) comparable to the electrode radius a are usually produced (Figure A). The current interest for such kinds of electrodes, other than for small-volume and microenvironment applications, , is largely driven by the use of microelectrodes as tips in scanning electrochemical microscopy (SECM). , In this technique, the parameter b/a , usually defined as RG, has strong influence on the Faradaic tip current, especially when the tip is moved in the vicinity of an inert substrate. , 1 Schematic representation of (A) electrode dimensions and simulation domain and (B) diffusion at a TSMs.…”
The cyclic voltammetric behavior of disk microelectrodes surrounded by thin insulating shields (TSM) was investigated from both theoretical and experimental points of view. In particular, microdisks with shields of thickness (b - a), a few electrode radii (a) were considered. A finite difference simulation procedure with a nonuniform, expanding spatial grid, already available in the literature, was employed for predicting shape and height of the voltammograms. The parameters of this numerical simulation were optimized again, and the steady-state limiting currents found in this work for a range of TSMs compared well with previous publications. The steady-state limiting current at TSMs was enhanced with respect to microelectrodes surrounded by thick insulating sheaths (i.e., b >> a), and steady-state conditions were achieved faster. Under these conditions, the difference in potential observed on the forward and backward waves, when the current is half of its maximum value (deltaE(1/2)), was almost equal to zero. Nonsteady-state cyclic voltammograms were also simulated using the optimized parameters, and the effect of scan rate on deltaE(1/2) was examined in detail. Based on this dependence, a voltammetric procedure for the simultaneous determination of microdisk radius and its insulator thickness was proposed. Experimental measurements were performed by using platinum wires, 10-12.5-microm radius, and carbon fibers, 4-microm radius, coated with 4-6-microm-thick electrophoretic paint. The shield thickness produced around the wires was such that b/a < 3. The experimental results obtained were in general congruent with the theory and demonstrated the validity of the method proposed here for the simultaneous determination of radius and shield thickness of a TSM.
“…The thin gate dielectric HfO 2 layer can be positioned on the top region using the atomic layer deposition (ALD) method [32]. In the next stage, utilizing the chemical vapor deposition process (CVD) [33], the metal electrodes (source, gate, and drain) have been developed on all sides of the active area. In the final stage, the metal electrode layer on the source side can be etched using a wet etching technique to create nanocavity.…”
Section: Biosensor Structure and Fabrication Processmentioning
This paper examines the sensitivity of a newly presented heterojunction dopingless tunnel field effect transistor (HJ-DLTFET) biosensor for the label-free detection of biomolecules. The etched nanocavity is introduced in the source metal region for better sensing ability. The dielectric constants (k) of five neutral biomolecules are employed in this paper to test the sensitivity of the proposed biosensor. The electrostatic performance is investigated based on transfer characteristics, energy band, tunneling distance (λ) at source/channel (S/C) interface, drain current (ID) variation for different dielectric constant (k), drain to source voltage (VDS) variation and mole fraction (x) variation respectively. Further, the RF performance analysis includes gate/source capacitance (Cgs), total gate capacitance (Cgg), cut-off frequency (ft), and maximum frequency (fm) analysis. Similarly, sensitivity analysis consists of current sensitivity (SID), current ratio sensitivity (Sratio), average SS sensitivity (SSS), Cgs sensitivity, Cgg sensitivity, ft sensitivity, and fm sensitivity. The investigation is carried out with the variation of neutral biomolecules in terms of various k inside the cavity. Similarly, the impact of charged biomolecules on the sensitivity of the proposed biosensor is investigated. The HJ-DLTFET sensor provides the maximum sensitivity SID of 1.56×1010, Sratio of 5.95×109, and SSS of 0.80 for Gelatin (k = 12.00) at room temperature using the Silvaco TCAD simulation tool. Combining a low band gap Si0.6Ge0.4 source with a high band gap silicon channel and a high-k (HfO2) improves drain current sensitivity without impacting leakage current.
“…Microeletrodos de disco podem também ser fabricados pela técnica de deposição química em fase vapor, [35][36][37][38][39][40][41] processo no qual a microfibra é isolada com uma fina camada de sílica. A formação do filme ocorre pela deposição da sílica a partir dos seus precursores gasosos (SiCl 4 , H 2 e O 2 ) ou pela deposição seqüencial de Si(OEt) 4 e dos precursores gasosos.…”
Section: Microeletrodos De Disco Fabricados a Partir Da Deposição Quíunclassified
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