Fishing – trapping – and vermin destroying
Patent
1991-01-14
1992-09-29
Larkins, William D.
Fishing, trapping, and vermin destroying
437101, 357 2, H01L 4500
Patent
active
051513846
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrical devices, and in particular to electrical switching devices.
A number of devices have been proposed in the art for switching between high and low resistance states. An amorphous silicon structure that switches from a low resistance to a high resistance state on application of an electrical potential above a given value is described for example by L. Mei and J. E. Greene, J. Appl. Phys Suppt. 2 Pt 1 (1974). However such a structure has the disadvantage that the ratio of the resistivity of the device in its high resistance state to that in its low resistance state is only 7:1, with the result that it would not be possible to form a useful switch for many purposes from such a material.
According to the present invention there is provided a method of producing an electrical device, which comprises: agent in order to remove or reduce the number of unpaired electrons occurring in the silicon compound; compound either before or after step (a); compound either before or after step (a); and silicon compound layer is restructured by passing an electric current through the device; layer which is adjacent to one of the electrodes and extends over part only of the device so that the maximum forming current passing through the device is limited to 400 mA.
The device produced according to the invention has the advantage that the electrical resistance of its high resistance state (or off state) is considerably increased with respect to the resistance of its low resistance state (or on state), with the result that the device may be employed for example as an electrical switch or an electrical fuse that will act as an electrical conductor but will switch to a high resistance state when it is subjected to an overvoltage or over-current. The device according to the invention has been observed to act as a threshold device, that is to say, it will change from a low resistance state to a high resistance state when subjected to a current or voltage above a given value, referred to as the threshold current or threshold voltage, but will remain in its high resistance state only for as long as the applied voltage is greater than a defined minimum value referred to as the holding voltage.
The switching material is preferably formed by reacting amorphous silicon, or an amorphous silicon compound e.g. amorphous silicon carbide, amorphous silicon nitride or amorphous silicon oxide, with the passivating agent, amorphous silicon preferably being employed.
The body of switching material will usually be in the form of a layer, in which case the electrodes may be located on opposite sides of the layer so that electrical current will pass through the layer. This may be achieved by a process in which steps (a) and (b) are conducted simultaneously by depositing a layer of the silicon or silicon compound on the first electrode in the presence of the passivating agent, followed by step (c). This form of device may instead be formed by depositing a layer of amorphous silicon or silicon compound on the first electrode followed by incorporating the passivating agent therein as explained below, and provision of the second electrode.
Alternatively both electrodes may be located on the same side of the layer of switching material so that electrical current will flow along one surface, or at least parallel to the surface, of the layer. This may be achieved by a process in which steps (b) and (c) are conducted simultaneously. The electrodes may be provided after the silicon or silicon compound layer has been formed or passivated, or the silicon or silicon compound layer may be deposited on the electrodes, reaction with the passivating agent being conducted simultaneously or subsequently as described elsewhere. A significant advantage of devices having both electrodes on the same side of the switching layer is that it is relatively easy to alter the electrode-electrode separation without affecting other manufacturing parameters such as the deposition time. It is possible by this means to have electrodes that are relativ
REFERENCES:
patent: 3271591 (1966-09-01), Ovshinsky
patent: 4226898 (1980-10-01), Ovshinsky et al.
patent: 4665428 (1987-05-01), Hockley et al.
J App Phys Support 2 pt 1 (1974), pp. 813-815 (Mei et al).
Rep Prog Phys, 33, (1970) pp. 1129-1191 (Stoneham et al).
Burkard Herbert G.
Larkins William D.
Raychem Limited
Richardson Timothy H. P.
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