The electrical characterization and response to hydrogen of Schottky diodes with a resistive metal electrode—rectifying an oversight in Schottky diode investigation

International audienceSchottky barrier structures with a resistive metal electrode are examined using the 4-point probe method where the probes are connected to the metal electrode only. The observation of a significant decrease in resistance with increasing temperature (over a range of ~ 100K) in the diode resistance-temperature (R D-T) characteristic is considered due to charge carrier confinement to the metal electrode at low temperature (high resistance), with the semiconductor progressively opening up as a parallel current carrying channel (low resistance) with increasing temperature due to increasing thermionic emission across the barrier. A simple model is constructed, based on thermionic emission at quasi-zero bias, that generates good fits to the experimental data. The negative differential resistance (NDR) region in the R D -T characteristic is a general effect and is demonstrated across a broad temperature range for a variety of Schottky structures grown on Si-, GaAs- and InP- substrates. In addition the NDR effect is harnessed in micro-scaled Pd/n-InP devices for the detection of low levels of hydrogen in an ambient atmosphere of nitrogen

Exploiting resistive macro to nano scale metal electrodes in Schottky barrier structures

This thesis investigates the use of thin resistive metal electrodes in the formation of Schottky barrier structures where the resistance measured along the electrode exhibits a characteristic change as a function of temperature dictated by the Schottky barrier properties. A combination of optical and resistance measurements (15-300K) on thin Al films were undertaken. Deviations of the real and imaginary parts of the . dielectric function from bulk valuek were significant for films thinner than ~15nm. The observed trend was confirmed by evaluating the resistivity data. The estimated thickness threshold for which the resistivity ratio (pjilm/pbulk) -- -I} became significantly greater than unity is ~8 nm for Al films. Thinner Al film showed poor inter-grain connectivity and a deteriorating interface quality. Resistance measurements on macro-scale Al and Pt electrodes and micro-scale Pt electrodes on p-type Si revealed a marked resistance increase by a factor of up to six over a temperature interval of 40-60K when decreasing temperature. The characteristic change of resistance is due to thermal confinement of charge carriers in the metal electrode, preventing any conduction channel through the substrate. This behaviour was modelled by considering the electrode and the substrate as two resistors in parallel with the Schottky barrier (barrier height determined by applying theory of thermionic emission) acting as the connecting component. The electrical and structural properties of Focused Ion Beam deposited Pt nanowires were analysed. EDX analysis revealed metal rich grains (atomic composition 31%Pt) in a large non-metallic matrix. Resistivity measurements (15-300K) indicated insulating behaviour with the room-temperature resistivity varying from 80 to 300 times higher than that of bulk Pt. Temperature dependent current-voltage measurements exhibited non-linear behaviour with the non-linearity increasing with decreasing temperature. The conduction mechanism can be explained in terms of a disordered solid with inter-grain tunnelling.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Exploiting resistive macro to nano scale metal electrodes in Schottky barrier structures

This thesis investigates the use of thin resistive metal electrodes in the formation of Schottky barrier structures where the resistance measured along the electrode exhibits a characteristic change as a function of temperature dictated by the Schottky barrier properties. A combination of optical and resistance measurements (15-300K) on thin Al films were undertaken. Deviations of the real and imaginary parts of the . dielectric function from bulk valuek were significant for films thinner than ~15nm. The observed trend was confirmed by evaluating the resistivity data. The estimated thickness threshold for which the resistivity ratio (pjilm/pbulk) -- -I} became significantly greater than unity is ~8 nm for Al films. Thinner Al film showed poor inter-grain connectivity and a deteriorating interface quality. Resistance measurements on macro-scale Al and Pt electrodes and micro-scale Pt electrodes on p-type Si revealed a marked resistance increase by a factor of up to six over a temperature interval of 40-60K when decreasing temperature. The characteristic change of resistance is due to thermal confinement of charge carriers in the metal electrode, preventing any conduction channel through the substrate. This behaviour was modelled by considering the electrode and the substrate as two resistors in parallel with the Schottky barrier (barrier height determined by applying theory of thermionic emission) acting as the connecting component. The electrical and structural properties of Focused Ion Beam deposited Pt nanowires were analysed. EDX analysis revealed metal rich grains (atomic composition 31%Pt) in a large non-metallic matrix. Resistivity measurements (15-300K) indicated insulating behaviour with the room-temperature resistivity varying from 80 to 300 times higher than that of bulk Pt. Temperature dependent current-voltage measurements exhibited non-linear behaviour with the non-linearity increasing with decreasing temperature. The conduction mechanism can be explained in terms of a disordered solid with inter-grain tunnelling.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Nanowires in electronics packaging

In the light of continuous miniaturization of traditional microelectronic components, the demand for decreasing wire diameters becomes immediately evident. The observation of metallic conductor properties for certain configurations of carbon nanotubes (CNT) and their current-carrying capability [1] sets the minimal diameter of a “true” wire to about 3 nm (compare Chap. 18). Investigations are in progress even below that diameter on nanocontacts, formed by single metal atoms, i.e. quantum wires. Quantum wires can be produced by mechanical wire breaking [2] or its combination with etching and deposition [3] or other techniques. The properties of quantum wires are only about to be understood theoretically [4]. Doubtless, they are worth considering for packaging solutions in molecular electronics to come [5]. In this chapter we focus on metal wires and rods in the size range above 10 nm up to submicron diameters, evaluated already to be attractive for microelectronic packaging purposes. Techniques to generate, to characterize and to handle them, as well as their interaction with electromagnetic fields will be useful for packaging applications in the age of nanotechnology. With the wealth of information available, this review focuses on general trends and starting points for deeper study. Although the cited references are representative, they cannot be complete, since numerous activities are still ongoing to produce and to characterize new kinds of wire-like geometries from different materials