Triangular Voltage Sweep Research Articles

Sodium Contamination in SiO2 Films Induced by Plasma Ashing

A sodium contamination phenomenon in a SiO2 film caused by O2 plasma ashing of a resist film was studied using the triangular voltage sweep method and neutron activation analysis. The contaminant sodium atoms have been proven to come from the resist film. The contamination occurs in two stages: (i) Before ashing end point, the sodium atoms dissolve only in the SiO2 surface layer by 1012 cm-2 surface area density or less. (ii) After the endpoint, the sodium amount in the SiO2 film increases markedly and eventually saturates at 1013–1014 cm-2. The sodium atoms in the SiO2 film migrate toward the SiO2/Si interface during over-ashing in O2 plasma. Ashing both in O2-CF4 plasma and in a metal shield cylinder are effective in reducing the sodium transportation rate and in preventing contamination.

On the mobility of potassium ions in SiO2

A new method to measure the mobility of K+ ions in SiO2 is proposed. The method is based on the TVS (triangular voltage sweep) technique at temperatures above 300 °C. The dependence of the voltage at which the current maximum occurs on the sweep rate provides the mobility at a particular temperature. Measurements at different temperatures show that the mobility of K+ ions in SiO2 can be described by μ (T) = (17.46/T) exp(−1.09/kT) cm2 V−1 s−1 in the temperature region 300–450 °C.

The relationship between the impedance of corroding electrode and its polarization resistance determined by a linear voltage sweep technique

The polarization resistance of metallic materials in contact with an electrolyte is largely used for the evaluation of its corrosion rate. The experimental value of polarization resistance is very often determined by plotting the polarization curves at the vicinity of the rest potential by a triangular voltage sweep technique. It is found that, for materials having high resistivity against corrosion, the value of polarization resistance is largely dependent on the sweep rate or the period of sweep cycle. If an equivalent circuit of a corroding electrode is to be presented by a parallel connexion of a resistance and a capacitance, such dependence of the polarization resistance cannot be explained at all. In fact, though the impedance of corroding electrode measured within a large frequency range shows one capacitive arc in the complex plane in accordance with parallel R—C circuit, the values of R and C both depend on frequency. The current response to a triangular voltage sweep signal is calculated numerically by Heaviside operational calculus using experimentally determined electrode impedance. A fairly good agreement was found between the experimental and calculated current—voltage cycles for different periods of a triangular voltage sweep signal.

Graphical technique to determine minority carrier lifetime and surface generation velocity using triangular-voltage sweep C-V method

A simple graphical technique has been developed to determine minority carrier lifetime and surface generation velocity simultaneously. This technique is based upon the high frequency C-V characteristics derived in response to a triangular-voltage sweep. The simultaneous determination of both parameters with error less than 5% is possible as long as the two generation processes have a comparable rate. The bulk lifetime τ B was measured over wide range of 10 nsec–10 msec, while surface generation velocity S can be measured over the range of 10 −3–10 3 cm/sec. There is little influence of the parasitic capacitance, which greatly affects the Zerbst plot. This technique is suitable for process characterization due to its simplicity.

Mobile ions in SiO2: Potassium

Mobile potassium ions have been conclusively identified in SiO2 using the high-temperature triangular voltage sweep technique, the bias temperature C-V technique, and ion microprobe studies. The source of the potassium has been found to be the tungsten filaments used for the aluminum gate metallization. Cautions regarding use of the high-temperature triangular voltage sweep technique for measuring mobile ions in MOS structures are discussed.

The current-voltage characteristics of MOS structures as measured with the triangular voltage sweep method : W. Marciniak and H. M. Przewlocki. Electron Technol. Warsaw8 (3/4), 19 (1975)

The current-voltage characteristics of MOS structures as measured with the triangular voltage sweep method : W. Marciniak and H. M. Przewlocki. Electron Technol. Warsaw8 (3/4), 19 (1975)

Determination of the double-layer capacity of porous nickel in KOH in the presence of faradaic current

Experimental and analytical techniques to determine the double-layer capacity of porous electrodes in the presence of faradaic effects are discussed. A triangular voltage sweep method was used with commercially available porous nickel plaque electrodes in KOH. No elaborate purification pretreatments were needed. A minimum double-layer capacity of about 28μF cm2 was determined at −0.40 V versus Hg/HgO which is close to the pzc reported for nickel. Overall the results agreed well with literature values for solid nickel.

The triangular voltage sweep method as a tool in studies of mobile charge in MOS structures

Formulae are derived allowing the analytic calculation of MOS structure quasi-equilibrium TVS current–voltage characteristics. It is assumed that mobile charges of one polarity are present in the dielectric layer which is held between two blocking electrodes. The voltage drop in the semiconductor electrode is taken into account. Characteristics calculated using the derived formulae are shown to be in good agreement with the experimental characteristics. A simplified method of mobile charge calculation, based on measurement of the current peak height is described, and a convenient way of checking whether proper measurement conditions were chosen is proposed. [Russian Text Ignored]

The Triangular Voltage Sweep Method for Determining Double‐Layer Capacity of Porous Electrodes: IV . Porous Carbon in Potassium Hydroxide

Triangular sweep voltammetry data for a number of commercially available carbons in 31 weight per cent are discussed. A capacity minimum of 10 μf/cm2 was observed about 0V vs. for five carbon blacks. Results indicated that the carbon blacks with internal structure were completely wetted; results with one activated carbon having fine micropores (<25Å) indicated partial wetting. Experimental methods for minimizing faradaic current and distributed capacity effects are discussed.

The oxygen electrode. Part 5.—Enhancement of charge capacity of an iridium surface in the anodic region

The anodic behaviour of iridium in the oxide layer region has been investigated using conventional electrochemical techniques such as cyclic voltammetry. Applying a triangular voltage sweep at 10 Hz, 0.01 to 1.50 V increases the amount of electric charge which the surface can store in the oxide region. This activation effect and the mechanism of charge storage is discussed in terms of both an expanded lattice theory for oxide growth on noble metals and a more recent theory of irreversible oxide formation with subsequent stoichiometry changes. The lack of hysteresis between the anodic and cathodic peaks at ca. 0.9 V suggests that the process involved here is proton migration in a relatively thick surface layer, i.e. that the reaction involved is some type of oxide-hydroxide transition. Lack of chloride ion inhibition in the anodic region also supports the irreversible oxide formation theory; however, to account for the hydrogen region of the potential sweep a compromise theory involving partial reduction of the outer regions of iridium oxide film is proposed. The loss of charge storage capacity when the activated iridium surface is anodized for a short time above ca. 1.60 V is attributed to loss by corrosion of the outer active layer from the metal surface.

The Triangular Voltage Sweep Method for Determining Double‐Layer Capacity of Porous Electrodes: III . Porous Nickel in Potassium Hydroxide

The effects of faradaic current and distributed capacity on the measurement of double‐layer capacity of porous nickel were analyzed as a function of electrode thickness and temperature. Faradaic current observed with electrodes at −46°C was negligible compared to results obtained at 22°C. Distributed capacity effects increased with electrode thickness and with decreasing temperature; the results agreed well with values predicted from a previously developed model. In the potential range of 0 to , the capacity based on the BET area of the electrode was about 30 µF/cm2.

Some pitfalls in fast ramp C- V measurements

The triangular voltage sweep or fast ramp C- V method, while leading to an easy measurement of deep depletion C- V curves, may have pitfalls for the unwary, particularly in the case of degraded oxides. Two examples of the difficulties associated with the measurement in the presence of positive oxide charge, viz., (i) a distorted fast ramp C- V curve at intermediate bias values and; (ii) a “peak” in the curve due to an inversion layer surrounding the device, are illustrated and explained.

The Triangular Voltage Sweep Method for Determining Double‐Layer Capacity of Porous Electrodes: II . Porous Silver in Potassium Hydroxide

One major problem in measuring the double‐layer capacity of a porous electrode is the effect of distributed reactions. Ohmic resistance of the electrolyte makes it easier to charge or discharge the outer surface of the electrode, while the interior lags behind. Triangular voltage sweep results obtained with porous silver in 31 weight per cent agreed well with predicted values obtained using a mathematical model which considers the physical properties of the electrode and electrolyte.

Zur anodischen auflösung von reineisen im bereich zwischen aktivem und passivem verhalten

The kinetics of anodic iron dissolution in sulphate ions containing solutions, which are free of oxygen, are investigated in a over potential range between active and passive states of the metal. The measurements were carried out on a rotating disk electrode in the pH-range between 3·5 and 5·5 using the potentiostatic triangular voltage sweep method under quasi-steady-state conditions. The measured current density-potential curves show two current maxima. At relatively low anodic overvoltages, i.e. before the maxima I is reached, the used recrystallized iron dissolves in the active state corresponding to the consecutive (Bockris-) mechanism. At high anodic overvoltages the passive state arises after passing the maxima II. In the transition range, i.e. in the potential range of the maximum I, a second mechanism of iron dissolution is discussed. This mechanism takes place parallel to the consecutive one. An intermediate [Fe (OH) 2] ads will be formed, which dissolves in a following rate-determining chemical step or is changed in an oxide phase respectively.

Zur Hemmung von Elektrodenvorgängen durch Grenzflächeninhibitoren—II. Metallionenübergänge

The kinetic of charge-transfer reactions at metal/ion electrodes and their inhibition by surface-active substances was studied in the system of a polarizable electrode (Au)/acid-solution, using the potentiostatic triangular voltage sweep method. By varying the sweep rate the experimental results can be explained by a consecutive charge-transfer mechanism in the case of the copper- and iron-electrode reactions. This corresponds to the theory of Bockris et al., eg two partial steps take place for the over-all reaction Me ⇄ Me 2+ + 2 e −. The charge-transfer reactions of metal ions are inhibited more than these of electrons by β-naphthoquinoline and dibenzylsulphoxide. Geometrical coverage is responsible for the inhibition of metal-ion charge-transfer reactions. The method gives qualitative results for the inhibition effects in systems of less polarizable metal electrodes (Cu, Fe)/acid-solution.

Application of Triangular Voltage Sweep Method to Mobile Charge Studies in MOS Structures

The present paper examines the theoretical aspects of the triangular voltage sweep (TVS) technique and describes the development of a unified quasi‐equilibrium approach wherein various polarization processes in an MOS capacitor structure subjected to the changing applied field are evaluated in terms of their contributions to the externally observed current. It is shown that a self‐consistent experimental and analytical approach must be used when the TVS technique is applied to mobile charge studies in MOS structures.

Anodische oxydation zu kohlendioxid von kohlenwasserstoffen, alkoholen und carbonsäuren an Raney-Platin

Knowledge of the mechanism involved in the anodic oxidation of hydrocarbons is of particular importance to the development of catalysts for low-temperature fuel cells. Galvanostatic measurements of current-voltage curves and potentiostatic-coulometric determinations of the conversion of hydrocarbons, alcohols, aldehydes, ketones and carboxylic acids in acid and alkaline electrolytes, performed on Raney platinum at temperature between 25 and 100°C, permit conclusions to be drawn on the reaction mechanism of the oxidation. The periodic current-voltage curves obtained by the triangular voltage sweep method show the differences in the sorption of hydrogen, oxygen, saturated and unsaturated hydrocarbons. In addition, the periodic current-voltage curves give indications of the mechanism involved. At open circuit, the saturated hydrocarbon is converted with water into hydrogen and carbon dioxide, the amount converted corresponding approximately to the thermodynamic equilibrium.

Significance of Nonsteady‐State A‐C and D‐C Measurements in Electrochemical Adsorption Kinetics: Applications to Galvanostatic and Voltage Sweep Methods

Information obtainable from nonsteady‐state electrochemical studies is examined with particular reference to the determination and significance of capacitance associated with adsorbed intermediates in consecutive reactions. The frequency dependence of the capacity in a‐c measurements is related to the rise‐time dependence in d‐c charging transients and the concept of an equivalent frequency in d‐c measurements is proposed. The nonsteady‐state kinetics for a galvanostatic charging process is examined for a reaction sequence involving adsorbed intermediates, and it is shown how the capacitance behavior depends on the charging current density. Applications to the triangular voltage sweep method are made, and it is shown that for this case where neither steady‐current nor steady‐state kinetics apply, care must be exercised in interpretation of results derived from this method. The nonsteady‐state kinetics for this case are derived and the dependence of the capacity on sweep‐rate is deduced. The differential galvanostatic method leads to results which can be much more explicitly analyzed in a rigorous kinetic manner, for irreversible charging processes. Applications to experimental results which support the treatment given are discussed.

The significance of measurements by the triangular voltage sweep method applied to adsorption reactions

The significance of measurements by the triangular voltage sweep method applied to adsorption reactions