Constant-amplitude RC oscillator

Sinusoidal oscillator has a frequency determined by resistance-capacitance /RC/ values of two charge control devices and a constant-amplitude voltage independent of frequency and RC values. RC elements provide either voltage-control, resistance-control, or capacitance-control of the frequency

Scanning Capacitance Spectroscopy on n\u3csup\u3e+\u3c/sup\u3e-p Asymmetrical Junctions in Multicrystalline Si Solar Cells

We report on a scanning capacitance spectroscopy (SCS) study on the n+-p junction of multicrystalline silicon solar cells. We found that the spectra taken at space intervals of ∼10 nm exhibit characteristic features that depend strongly on the location relative to the junction. The capacitance-voltage spectra exhibit a local minimum capacitance value at the electrical junction, which allows the junction to be identified with ∼10-nm resolution. The spectra also show complicated transitions from the junction to the n-region with two local capacitance minima on the capacitance-voltage curves; similar spectra to that have not been previously reported in the literature. These distinctive spectra are due to uneven carrier-flow from both the n- and p-sides. Our results contribute significantly to the SCS study on asymmetrical junctions

Role of Contacts in Capacitance Measurements of Solar Cells

The electronic properties of low cost, thin-film solar cells are complicated by the non-ideal nature of the semiconductor layers. Typically, the fundamental electronic properties of such materials are evaluated using current-voltage and capacitance-voltage measurements. However, in these devices, it is common for the back contact to be non-ohmic. We are exploring the impact of such a back contact on the outcome of standard capacitance-based characterization techniques. We compare computer models of capacitance response with measurements of simple model electronic circuits and of solar cell devices

Observation of quantum capacitance in the Cooper-pair transistor

We have fabricated a Cooper-pair transistor (CPT) with parameters such that for appropriate voltage biases, the sub-gap charge transport takes place via slow tunneling of quasiparticles that link two Josephson-coupled charge manifolds. In between the quasiparticle tunneling events, the CPT behaves essentially like a single Cooper-pair box (SCB). The effective capacitance of a SCB can be defined as the derivative of the induced charge with respect to gate voltage. This capacitance has two parts, the geometric capacitance, C_geom, and the quantum capacitance C_Q. The latter is due to the level anti-crossing caused by the Josephson coupling. It depends parametrically on the gate voltage and is dual to the Josephson inductance. Furthermore, it's magnitude may be substantially larger than C_geom. We have been able to detect C_Q in our CPT, by measuring the in-phase and quadrature rf-signal reflected from a resonant circuit in which the CPT is embedded. C_Q can be used as the basis of a charge qubit readout by placing a Cooper-pair box in such a resonant circuit.Comment: 3 figure

Characteristics of arc currents on a negatively biased solar cell array in a plasma

The time dependence of the emitted currents during arcing on solar cell arrays is being studied. The arcs are characterized using three parameters: the voltage change of the array during the arc (i.e., the charge lost), the peak current during the arc, and the time constant describing the arc current. This paper reports the dependence of these characteristics on two array parameters, the interconnect bias voltage and the array capacitance to ground. It was found that the voltage change of the array during an arc is nearly equal to the bias voltage. The array capacitance, on the other hand, influences both the peak current and the decay time constant of the arc. Both of these characteristics increase with increasing capacitance