Showing papers on "Conductance published in 1985"

Generalized many-channel conductance formula with application to small rings.

Abstract: The conductance of a sample scattering elastically and coupled to leads with many channels is derived. We assume that all the incident channels on one side of the sample are fed from the same chemical potential. The transmitted and reflected streams are determined by the incident streams through the multichannel scattering properties of the sample. We do not assume that the channels equilibrate with each other. Our result differs from those given earlier by other authors, except for that of Azbel [J. Phys. C 14, L225 (1981)], which is confirmed. We point out that a similar result is obtained for the conductance in a single channel at a temperature above zero. As an application, we obtain the dependence on channel number N of the contributions to the conductance of a small ring, periodic in the Aharonov-Bohm flux through it. Terms whose period is h/e as well as those with period h/2e vary with N as 1/N.

Light-suppressible, cyclic GMP-sensitive conductance in the plasma membrane of a truncated rod outer segment

Abstract: Recent experiments by Fesenko et al and ourselves have shown that excised membrane patches from retinal rod outer segments contain a cyclic GMP-sensitive conductance which has electrical properties similar to those of the light-sensitive conductance. This finding supports the notion that cGMP mediates phototransduction (see ref. 3) by directly modulating the light-sensitive conductance. However, some uncertainty remained about whether the patch experiments had discriminated completely between plasma and intracellular disk membranes; thus the cGMP response in an excised membrane could have resulted from contaminating disk membrane fragments, which are known to contain a cGMP-regulated conductance. Furthermore, the patch conductance has not yet been shown to be light-suppressible, an ultimate criterion for identity with the light-sensitive conductance. We now report experiments on a truncated rod outer segment preparation which resolved these issues. The results demonstrated that the cGMP-sensitive conductance was present in the plasma membrane of the outer segment, and that in the presence of GTP the conductance could be suppressed by a light flash. With added ATP, the effectiveness of the light flash was reduced and the suppression was more transient. The effects of both GTP and ATP were consistent with the known biochemistry. From the maximum current inducible by cGMP, we estimate that approximately 1% of the light-sensitive conductance is normally open in the dark; this would give an effective free cGMP concentration of a few micromolar in the intact outer segment in the dark.

Cyclic GMP-sensitive conductance in outer segment membrane of catfish cones

Abstract: A cyclic GMP-sensitive conductance has recently been observed with patch-clamp recording in excised inside-out patches of plasma membrane from frog and toad rod outer segments This conductance has properties suggesting that it is probably the light-sensitive conductance involved in visual transduction We now report a similar conductance in the outer segment membrane of catfish cones Cyclic GMP showed positive cooperativity in opening this conductance, with a Hill coefficient of 16-30 and a half-saturating cGMP concentration of 35-70 microM Cyclic AMP at 1 mM, or changing Ca concentration (in the presence of Mg), had little effect on the conductance In physiological solutions the cGMP-induced current had a reversal potential near +10 mV; the current amplitude increased roughly exponentially with membrane potential in both depolarizing and hyperpolarizing directions Our results suggest that cGMP is also the internal transmitter for phototransduction in cones

ATP-sensitive inward rectifier and voltage- and calcium-activated K+ channels in cultured pancreatic islet cells.

Abstract: K+ channels in cultured rat pancreatic islet cells have been studied using patch-clamp single-channel recording techniques in cell-attached and excised inside-out and outside-out membrane patches. Three different K+-selective channels have been found. Two inward rectifier K+ channels with slope conductances of about 4 and 17 pS recorded under quasi-physiological cation gradients (Na+ outside, K+ inside) and maximal conductances recorded in symmetrical K+-rich solutions of about 30 and 75 pS, respectively. A voltage- and calcium-activated K+ channel was recorded with a slope conductance of about 90 pS under the same conditions and a maximal conductance recorded in symmetrical K+-rich solutions of about 250 pS. Single-channel current recording in the cell-attached conformation revealed a continuous low level of activity in an apparently small number of both the inward rectifier K+ channels. But when membrane patches were excised from the intact cell a much larger number of inward rectifier K+ channels became transiently activated before showing an irreversible decline. In excised patches opening and closing of both the inward rectifier K+ channels were unaffected by voltage, internal Ca2+ or externally applied tetraethylammonium (TEA) but the probability of opening of both inward rectifier K+ channels was reduced by internally applied 1-5 mM adenosine-5'-triphosphate (ATP). The large K+ channel was not operational in cell-attached membrane patches, but in excised patches it could be activated at negative membrane potentials by 10(-7) to 10(-6) M internal Ca2+ and blocked by 5-10 mM external TEA.

Effect of phospholipid surface charge on the conductance and gating of a Ca2+-activated K+ channel in planar lipid bilayers

Abstract: A Ca-activated, K-selective channel from plasma membrane of rat skeletal muscle was studied in artificial lipid bilayers formed from either phosphatidylethanolamine (PE) or phosphatidylserine (PS). In PE, the single-channel conductance exhibited a complex dependence on symmetrical K+ concentration that could not be described by simple Michaelis-Menten saturation. At low K+ concentrations the channel conductance was higher in PS membranes, but approached the same conductance observed in PE above 0.4m KCl. At the same Ca2+ concentration and voltage, the probability of channel opening was significantly greater in PS than PE. The differences in the conduction and gating, observed in the two lipids, can be explained by the negative surface charge of PS compared to the neutral PE membrane. Model calculations of the expected concentrations of K+ and Ca2+ at various distances from a PS membrane surface, using Gouy-Chapman-Stern theory, suggest that the K+-conduction and Ca2+-activation sites sense a similar fraction of the surface potential, equivalent to the local electrostatic potential at a distance of 9 A from the surface.

Mechanotransducer ion channels in chick skeletal muscle: the effects of extracellular pH.

Abstract: The membrane of tissue-cultured chick pectoral muscle contains an ionic channel which is activated by membrane tension. With 150 mM-external K+ and 150 mM-internal Na+, the channel has a conductance of 70 pS and a reversal potential of +30 mV. With 150 mM-external Na+ and 150 mM-internal K+ (normal gradient) the channel has a conductance of 35 pS and a reversal potential of -30 mV. The ratio of K+ permeability to Na+ permeability, PK:PNa, is 4 based upon reversal potentials and is 2 based upon conductance. Kinetic analysis of single-channel records indicates that there are one open (O) and three closed (C) states. When analysed according to a linear sequential model: C1-C2-C3-O4, only the rate constant that governs the C1-C2 transition (k1,2) is found to be affected by stretch or voltage. The effects of stretch and voltage on k1,2 can be summarized as k1,2 = k1,2(0) exp (alpha V + theta P2), where K1,2(0) is the voltage and stretch-independent part of the rate constant, alpha is the voltage sensitivity, V is the transmembrane potential, theta is the stretch sensitivity and P is the applied suction. Increasing extracellular pH from 7.4 to 10.0 increases both alpha and theta in a manner suggesting titration of site(s) with a pK of 9.1. A single lysine of N-terminal amino acid may be be responsible for modulating both the voltage and pressure responses. Extracellular pH does not affect k1,2(0), the voltage- and stretch-independent part of k1,2, suggesting that pH in the range 7.4-10 does not alter the local surface charge. The conductance and reversal potential of the s.a. channel are unaffected by pH, suggesting that the titrated site(s) is not close to the mouth of the channel.

Regulation of gap junctional conductance.

Abstract: Gap junctional conductance is regulated by the number of channels between coupled cells (the balance between formation and loss of these channels) and by the fraction of these channels that are open (gating mechanisms). A variety of treatments are known to affect junction formation. Adenosine 3',5'-cyclic monophosphate (cAMP) is involved in some cases, and protein synthesis may be required but precursor molecules can also exist. Junction removal occurs both by dispersion of particles and by internalization of junctional membrane. Factors promoting removal are not well understood. A variety of gating mechanisms exist. Coupling may be controlled by changes in conductance of nonjunctional membranes. Several kinds of voltage dependence of junctional conductance are known, but rat ventricular junctions at least are electrically linear. Cytoplasmic acidification decreases conductance of most gap junctions. Sensitivity in rat ventricular myocytes allows modulation of coupling by moderate changes near normal internal pH. Increasing intracellular Ca also decreases junctional conductance, but in the better studied cases sensitivity is much lower to Ca than H. A few data support low sensitivity to Ca in cardiac cells, but quantitative studies are lacking. Higher alcohols such as octanol block junctional conductance in a wide range of tissues including rat ventricular myocytes. An antibody to liver gap junctions blocks junctions between rat ventricular myocytes. Cross reactivity indicates at least partial homology between many gap junctions. Although differences among gap junctions are known, a general physiology is being developed, which may have considerable relevance to normal cardiac function and also to conduction disorders of that tissue.

Single Cl- channels in molluscan neurones: multiplicity of the conductance states.

Abstract: Properties of the single Cl− channels were studied in excised patches of surface membrane from molluscan neurones using single-channel recording technique. These channels are controlled by Ca2+ and K+ acting on cytoplasmic and outer membrane surfaces, respectively, and by the membrane potential. The channels display about 16 intermediate conductance sublevels, each of them being multiples of ∼12.5 pS. The upper level of the channel conductance is about 200 pS. The channel behavior is consistent with an aggregation of channel-forming subunits into a cluster.

Electrophysiology of flounder intestinal mucosa. I. Conductance properties of the cellular and paracellular pathways.

Abstract: We evaluated the conductances for ion flow across the cellular and paracellular pathways of flounder intestine using microelectrode techniques and ion-replacement studies. Apical membrane conductance properties are dominated by the presence of Ba-sensitive K channels. An elevated mucosal solution K concentration, [K]m, depolarized the apical membrane potential (psi a) and, at [K]m less than 40 mM, the K dependence of psi a was abolished by 1-2 mM mucosal Ba. The basolateral membrane displayed Cl conductance behavior, as evidenced by depolarization of the basolateral membrane potential (psi b) with reduced serosal Cl concentrations, [Cl]s. psi b was unaffected by changes in [K]s or [Na]s. From the effect of mucosal Ba on transepithelial K selectivity, we estimated that paracellular conductance (Gp) normally accounts for 96% of transepithelial conductance (Gt). The high Gp attenuates the contribution of the cellular pathway to psi t while permitting the apical K and basolateral Cl conductances to influence the electrical potential differences across both membranes. Thus, psi a and psi b (approximately 60 mV, inside negative) lie between the equilibrium potentials for K (76 mV) and Cl (40 mV), thereby establishing driving forces for K secretion across the apical membrane and Cl absorption across the basolateral membrane. Equivalent circuit analysis suggests that apical conductance (Ga approximately equal to 5 mS/cm2) is sufficient to account for the observed rate of K secretion, but that basolateral conductance (Gb approximately equal to 1.5 mS/cm2) would account for only 50% of net Cl absorption. This, together with our failure to detect a basolateral K conductance, suggests that Cl absorption across this barrier involves KCl co-transport.

Single-file diffusion through the Ca2+-activated K+ channel of human red cells.

Abstract: The ratio between the unidirectional fluxes through the Ca2+-activated K+-specific ion channel of the human red cell membrane has been determined as a function of the driving force (Vm-EK). Net effluxes and 42K influxes were determined during an initial period of approximately 90 sec on cells which had been depleted of ATP and loaded with Ca. The cells were suspended in buffer-free salt solutions in the presence of 20 microM of the protonophore CCCP, monitoring in this way changes in membrane potential as changes in extracellular pH. (Vm-EK) was varied at constant EK by varying the Nernst potential and the conductance of the anion and the conductance of the potassium ion. In another series of experiments EK was varied by suspending cells in salt solutions with different K+ concentrations. At high extracellular K+ concentrations both of the unidirectional fluxes were determined as 42K in- and effluxes in pairs of parallel experiments. Within a range of (Vm-EK) of -6 to 90 mV the ratio between the unidirectional fluxes deviated strongly from the values predicted by Ussing's flux ratio equation. The Ca2+-activated K+ channel of the human red cell membrane showed single-file diffusion with a flux ratio exponent n of 2.7. The magnitude of n was independent of the driving force (Vm-EK), independent of Vm and independent of the conductance gK.

Fertilization-induced ionic conductances in eggs of the frog, Rana pipiens.

Abstract: Fertilization of the frog egg (Rana pipiens) elicits a positive-going shift in membrane potential (fertilization potential) that lasts 10-20 min and functions as a fast block to polyspermy. We examined the ion conductances underlying the fertilization potential, using the voltage-clamp technique. We measured the membrane capacitance during the fertilization potential by applying an alternating current. We also determined the intracellular K and Cl concentrations in the egg, using ion-selective micro-electrodes. The conductance is largest in the first 2 min after fertilization. Regardless of whether the stimulus is provided by one or by more than one sperm or by artificial activation, the size of the conductance increase is the same, reaching a maximum of about 40 microseconds. Two separate conductances are involved at fertilization: Cl and K. [K]i = 121 mM and [Cl]i = 44 mM. The natural external medium is pond water (approximated in our experiments by 10% Ringer solution); therefore, an increase in K and Cl conductances leads to an efflux of both ions. The equilibrium potential of the fertilization current is between the Cl and K equilibrium potentials (ECl and EK), closer to ECl. 10 mM-external tetraethylammonium (TEA) brings the equilibrium potential close to ECl and reduces the maximum conductance by about half. The Cl conductance is not blocked by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid (SITS). The time courses of the K and Cl conductances are similar. The TEA-resistant conductance (primarily Cl conductance) activated at fertilization increases as the membrane potential becomes more positive. A voltage-sensitive Na conductance present in the unfertilized egg disappears after fertilization. During fertilization this conductance is too small to contribute significantly to the fertilization potential. The membrane capacitance increases by an average of 1.9 times in the first 2 min following the rise of the fertilization potential, during the period of cortical vesicle exocytosis. Capacitance then gradually decreases; at 1 h after fertilization, capacitance is 82% of the value in the unfertilized egg. The conductance increase precedes the capacitance increase by several seconds. Therefore the initial appearance of Cl and K channels cannot be accounted for by addition of membrane by cortical vesicle exocytosis. The conductance subsequently decreases, suggesting that the disappearance of the Cl and K channels is not caused by membrane removal.

Ionic conductivity and microwave dielectric relaxation of lithium hexafluoroarsenate (LiAsF6) and lithium perchlorate (LiClO4) in dimethyl carbonate

Abstract: : Audiofrequency electrical conductivity data are reported in the solvent dimethylcarbonate (DMC) at 25 deg C in the concentration range 00001 to 1M for LiAsF6 and 00001 to 03M for LiClO4 From 00001 to approx = 001M the data are interpreted by the Fuoss-Kraus triple-ions theory leading to the values of the ion pair formation constant Kp and triple ion formation constant KT For the data at higher concentration, it is shown that the change of static permittivity of the solution (due to the presence of solute ion-pairs and other polar species, which increase the polarization of the solution) can account qualitatively for the behavior of the conductance data and their deviation from the Fuoss-Kraus theory These deviations are mostly due to changes in permittivity, not accounted for in the conventional treatment of the data, rather than by the failure of the theory Introduction of the quadrupole formation constant is necessary, however, for LiAsF6 for a more quantiative treatment of the conductance data Microwave complex permitivities in the concentration range 005M to 03M, frequency range approx = 1 to 90- GHz are intepreted by two Debye relaxation processes, one due to the solute and one to the solvent For LiAsF6 the Boettcher plot, (expressing a quantity related to the change of the relaxation strength with the concentration of electrolyte), is nonlinear with the concentration Keywords include: Electrical conductance, and Microwave dielectric relaxation

Origin of the Peaked Structure in the Conductance of One-Dimensional Silicon Accumulation Layers

Abstract: We have made extensive studies of the temperature, gate voltage, and electric field dependences of the conductance peaks in small silicon inversion layers in order to distinguish between resonant-tunneling models and a hopping model. We find that many of the peaks are consistent only with a hopping model, whereas some could be consistent with an early resonant-tunneling model. None of our structure is consistent with resonant tunneling if the recent formulation of Stone and Lee is correct.

Gap junction structures after experimental alteration of junctional channel conductance.

Abstract: Gap junctions are known to present a variety of different morphologies in electron micrographs and x-ray diffraction patterns. This variation in structure is not only seen between gap junctions in different tissues and organisms, but also within a given tissue. In an attempt to understand the physiological meaning of some aspects of this variability, gap junction structure was studied following experimental manipulation of junctional channel conductance. Both physiological and morphological experiments were performed on gap junctions joining stage 20-23 chick embryo lens epithelial cells. Channel conductance was experimentally altered by using five different experimental manipulations, and assayed for conductance changes by observing the intercellular diffusion of Lucifer Yellow CH. All structural measurements were made on electron micrographs of freeze-fracture replicas after quick-freezing of specimens from the living state; for comparison, aldehyde-fixed specimens were measured as well. Analysis of the data generated as a result of this study revealed no common statistically significant changes in the intrajunctional packing of connexons in the membrane plane as a result of experimental alteration of junctional channel conductance, although some of the experimental manipulations used to alter junctional conductance did produce significant structural changes. Aldehyde fixation caused a dramatic condensation of connexon packing, a result not observed with any of the five experimental uncoupling conditions over the 40-min time course of the experiments.

Effect of fluid pressure on the hydraulic conductance of interstitium and fenestrated endothelium in the rabbit knee.

Abstract: A synovial cavity is separated from plasma by synovial intima in series with capillary endothelium. Because 20% of the intimal surface is bare interstitium, the system is a convenient model for the study of passive transport through serial endothelial and interstitial layers. Here hydraulic flow across the composite barrier was investigated in forty-seven knees of isolated, blood-perfused rabbit hindquarters, at intra-articular pressures between 4 and 30 cmH2O. In order to measure barrier conductance at constant intra-articular pressure, pressure on the opposite side of the barrier was varied, i.e. capillary blood pressure (PC). Capillary pressure was changed by alteration of vascular perfusion pressures, and the resulting changes in rate of absorption of Krebs solution from the synovial cavity (QS) were recorded. Trans-synovial absorption was a negative linear function of PC at each joint pressure, in verification of the applicability of Starling's hypothesis to this system. The hydraulic conductance of the blood-joint barrier was calculated as dQS/dPC. Conductance was independent of intra-articular pressure below 9 cmH2O and was 0.12 +/- 0.015 microliter min-1 mmHg-1 (mean +/- S.E. of mean). Barrier conductance increased as a curvilinear function of intra-articular pressure above 9.4 cmH2O (yield pressure). At 30 cmH2O conductance averaged 0.60 +/- 0.06 microliter min-1 mmHg-1, a 5-fold increase. A hyperbolic curve relating net barrier conductance to joint pressure was predicted from the hypothesis that interstitial conductance increases as a monotonic function of intra-articular pressure above yield pressure (Appendix). The data were in reasonable agreement with the theoretical hyperbola. Interstitial conductivity (3 X 10(-7)-7 X 10(-7) cm4 s-1 N-1 below yield pressure) and mean endothelial conductance (1.1 X 10(-4)-1.4 X 10(-4) cm3 s-1 N-1) were evaluated and compared with values in other tissues. Synovial endothelium contains on average 0.25 fenestrae micron-1 circumference. The conductance of a single fenestra was calculated to be 2.3 X 10(-13) cm5 s-1 N-1. Interstitial resistance accounted for roughly half the total resistance below yield point: therefore dQS/dPC should not be equated with 'capillary filtration capacity' in tissues with dense or fenestrated capillary beds. Large inconsistencies between interstitial conductivity and glycosaminoglycan concentration are noted, and mechanistic explanations of increases in conductivity with joint pressure are offered.

Thermal conductance and giant fluctuations in one-dimensional disordered systems.

Abstract: The thermal conductance for the energy transport through a disordered harmonic chain is calculated by a tunneling expression of the energy current The dominant contribution comes from quasiballistic phonons for which the localization length is comparable to the size of the chain A universal regime of conductance in ${k}_{B}^{2}$T/\ensuremath{\Elzxh} is obtained at low temperature, while giant fluctuations are predicted at higher temperature Analogies with electrical conductance are established and conditions for measurements are discussed

A kinetic analysis of the electrogenic pump of Chara corallina : III. Pump activity during action potential

Abstract: The current-voltage curve (I–V curve) of theChara membrane was obtained by applying a slow ramp hyper- and depolarization by use of voltage clamp. By inhibiting the electrogenic pump with 50μm DCCD (dicyclohexylcarbodiimide), theI–V curve approached a steadyI–V curve within two hours, which gave thei d -V curve of the passive diffusion channel. Thei p -V curve of the electrogenic pump channel was obtained by subtracting the latter from the former. The sigmoidali p -V curve could be simulated satisfactorily with a simple reaction kinetic model which assumes a stoichiometric ratio of 2. The emf of the pump (E p ) is given as the voltage at which the pump current changes its sign. The conductance of the pump (g p ) can be calculated as the chord conductance from thei p -V curve, which is highly voltage dependent having a peak at a definite voltage. The changes of emf and conductance during excitation were determined by use of the current clamp (I=0). Since theE p andg p (V) are known, the changes, during excitation, of emf (E d ) and conductance (g d ) of the passive diffusion channel can be calculated. The marked increase of the membrane conductance and the large depolarization during the action potential are caused by the marked increase of the conductance of the passive diffusion channel and the large depolarization of its emf. The conductance of the electrogenic pump decreases to about half at the peak of action potential, while the pump current increases almost to a saturated level.

Synaptic block of a calcium-activated potassium conductance in Aplysia neurones.

Abstract: In the preceding paper (Kehoe, 1985) it was shown that the firing of any one of three neurones (I, II, III) presynaptic to the medial cells of the pleural ganglion of Aplysia californica causes a diminution of the cholinergically controlled K conductance in those cells. Firing of the same three presynaptic neurones was shown here to cause a similar diminution in a depolarization-induced K-dependent conductance in the same post-synaptic cells. The depolarization-induced K conductance was found to disappear when Ca ions were removed from the sea water bathing the ganglion or when the cell was injected with the Ca chelator ethyleneglycol-bis-(beta-aminoethylether)N,N'-tetra-acetic acid (EGTA). The diminution in this Ca-activated, K-dependent current occurred even when the presynaptic neurone was fired a few seconds after the end of the depolarizing voltage step to the post-synaptic neurone, showing that the diminution in K conductance was not an indirect effect of a transmitter-induced diminution in Ca influx during the depolarizing pulse. The two K conductances affected by the 'blocking neurones' could be selectively eliminated. The cholinergic conductance could be blocked by receptor-specific cholinergic antagonists (e.g. 1 mM concentrations of phenyltrimethylammonium (PTMA), choline and tetraethylammonium (TEA]. Even at 10 mM concentrations, none of these compounds (including TEA, which is known to block certain Ca-activated K conductances) had an effect on the depolarization-induced, Ca-activated K conductance studied here. This latter conductance, on the other hand, was selectively blocked by an intracellular injection of EGTA. The three blocking neurones continued to diminish the K conductance (cholinergic or depolarization induced) that remained intact under these different experimental conditions. The depolarization-induced influx of Ca was shown to block the cholinergically controlled K conductance, but Ca was excluded as the possible mediator of the diminution in K conductance caused by the three blocking neurones. An intracellular injection of Ca ions into the medial cells was shown to activate a variety of changes in membrane conductance; in particular, two K-conductance increases: an early, TEA-sensitive one, and a slowly developing, TEA-insensitive one. Both the permeant cyclic AMP analogue p-chlorophenylthioadenosine 3',5'-monophosphate (CPT-cyclic AMP) and the phosphodiesterase inhibitors amino-phylline and isobutyl-1-methylxanthine (IBMX) were shown to block the depolarization-induced K conductance, and to reduce, though not eliminate, the slowly developing K conductance activated by an intracellular injection of Ca.(ABSTRACT TRUNCATED AT 400 WORDS)

Gap junction ultrastructure in three states of conductance

Abstract: Junctional conductance between the epidermal cells of the beetle Tenebrio molitor is raised after exposure to the hormone 20-hydroxyecdysone and lowered reversibly by exposure to chlorpromazine. Gap Junctional particle size, density and arrangement associated with these conductance changes were studied. We found no significant difference in particle density in gap junctions of control (2456±471 particles/μm2, mean ±S.D.) and hormone-treated epidermis (2490±315); however, a significant increase in packing density occurred in chlorpromazine-uncoupled epidermis (3133±665). The particles are randomly arranged in all three states of conductance. Particle size measurements show that the E-face gap junctional particles are heterogeneous with a mean diameter ±S.D. of 15.2±2.0 nm. No significant difference in particle size between controls and experimentals was detected. Although glutaraldehyde irreversibly uncoupled these cells, the absence of glutaraldehyde fixation but presence of glycerol induced marked alterations in the appearance of the gap junctions such that quantification was no longer possible. From this particle-packing data and our previous thin-section data, we estimate that there are 90000 gap junctional particles per cell (within junctional plaques). The conductance of a single gap junctional channel (assuming one population) changes from 94 pS to 213 pS after hormone treatment.

Characterization of Si‐SiO2 interface states: Comparison between transient capacitance and conductance techniques

Abstract: The conductance versus frequency technique [G(ω)] and deep level transient spectroscopy (DLTS) are both used to characterize Si‐SiO2 interface states. However, no direct comparison between the two methods has yet been performed. We have performed a systematic study, with these two techniques of the same metal oxide semiconductor structures (Si‐SiO2 on n‐ and p‐type materials) made with various technologies and we have compared the performances of each technique: energy range accessible, energy resolution, sensitivity. We have shown that the conductance technique provides a density of states larger than the one obtained by DLTS, that its sensitivity and energy range are smaller. Its energy resolution is also smaller as illustrated by the fact that localized levels are detected by DLTS which are not with the conductance technique.