Patent Application
20170200815
The Casimir effect is a nonlinear attractive force between conducting plates that arises from a quantized vacuum field around the plates. Such a force can be induced by virtual photons that fill the vacuum field, and the induced force varies based on the separation between the conducting surfaces of the plates. Certain photon modes are forbidden from the area of the separation between the plates (i.e. photon modes of wavelengths that are too large to fit within the separation). Due to this phenomenon, the energy density is lower between the plates than it is outside the plates, and a pressure is formed that pushes the plates together.
One embodiment relates to a method of controlling a Casimir-effect device. The Casimir-effect device comprises a conducting layer and a semiconducting layer, where the conducting layer and semiconducting layer are separated by a gap. The method includes applying an electric field to at least a portion of the semiconducting layer of the Casimir-effect device, via a voltage applied to an electrode, which forms a field-effect gate over at least a portion of the semiconducting layer facing the gap. The method further includes varying, in response to the applied voltage, a charge density of a surface portion of the semiconducting layer facing the gap to control a nanoscale Casimir force between the conducting layer and the surface portion of the semiconducting layer facing the gap. In response to the applied voltage, the surface portion of the semiconducting layer may vary from essentially conducting to essentially non-conducting.
Another embodiment relates to a Casimir-effect device. The device comprises a conducting layer and a semiconducting layer, where the conducting layer and semiconducting layer are separated by a gap. An electric field can be applied to the semiconducting layer to vary a charge density of a surface portion of the semiconducting layer, such that the surface portion of the semiconducting layer may vary from essentially conducting to essentially non-conducting. In some embodiments, the device comprises a moveable element. The moveable element may comprise the conducting layer or the semiconducting layer. The device further comprises a second semiconducting layer, wherein the moveable element is separated by a gap from the second semiconducting layer, and wherein the moveable element is configured to move in response to a Casimir force formed between the moveable element and the second semiconducting layer.
Another embodiment relates to a method of manufacturing a Casimir-effect device. The method comprises providing a conducting material. The method further comprises providing a second element comprising a semiconductor wherein the conducting material is separated by a gap from the second element. The method further comprises providing at least one electrode configured to apply an electric field to the semiconductor to vary a charge density of a surface portion of the semiconductor, such that the surface portion of the semiconductor varies from essentially conducting to essentially non-conducting.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the scope of the subject matter presented here.
Referring generally to the figures, various embodiments of a Casimir-effect transistor devices are shown and described. The Casimir-effect is an attractive force that arises in a vacuum space, which is filled by virtual photons. In general, the modes of the virtual photons are uniform in density, and there is no Casimir-effect. However, if two conducting surfaces are introduced into the space and the conducting surfaces are arranged sufficiently close together (e.g., parallel) to form a cavity therebetween, photon modes of wavelengths that are larger than the cavity cannot exist within the cavity. As a result, the energy density (i.e., the virtual radiation from the virtual photons) is lower in the cavity than it is outside the conducting surfaces, which materializes as a pressure from the higher energy density outside the cavity that pushes the surfaces together.
Although the resulting Casimir force is present, it is typically negligible until the conducting surfaces are spaced sufficiently close together. The Casimir force is non-linear, and is inversely proportional to the fourth power of the separation between the conducting surfaces (the Casimir force varies according to L−4, where L equals the separation between the conducting surfaces). Thus, to obtain a measureable effect, the conducting surfaces generally need to be spaced at a separation on the nanometer scale (or smaller). An example physical scale at which the Casmir force is significant is for a conducting surface spacing of 10 nanometers. In the embodiments described herein, the Casimir-effect can be switched on and off (or modulated), for example, by altering the conductivity of one or more of the conducting surfaces. By controlling the conductivity, the Casimir force may be increased or reduced as desired.
Referring to
Referring to
In some embodiments, a field-effect gate 206 is formed over at least a portion of semiconducting material 204, which may be used to control a Casimir force between conducting material 202 and semiconducting material 204. For example, a voltage can be applied to the field-effect gate 206 to alter the density of free charge carriers in a portion of semiconducting material 204 facing the gap. The field-effect gate 206 may be formed in various ways. In one embodiment, the field-effect gate 206 is formed by the conducting material 202 itself, which is insulated from semiconducting material 204 by the gap. In another embodiment, the field effect gate 206 is formed by a differently-doped region in contact with the semiconducting material 204. For example, the field effect gate 206 may include a portion of the semiconductor material 204. The field effect gate 206 may comprise the rear surface portion of the semiconducting layer having a different doping from the remainder of the semiconductor layer, and isolated from the remainder of the semiconductor layer by a P-N junction or a P-I-N junction. In another embodiment, the field-effect gate 206 is formed by an electrode that is insulated from semiconducting material 204 (e.g., semiconducting material 204 may comprise the channel of a metal-oxide-semiconductor-field-effect transistor (MOSFET)). Other known methods of forming field-effect gate 206 may also be utilized to alter the density of free charge carriers in the portion of semiconducting material 204 facing the gap.
Referring to
In one embodiment, second element 304 includes a surface that is nominally flat and moveable element 302 includes a conducting area that is parallel to the surface of second element 304. Moveable element 302 may be a conducting area on the surface of a disk or plate, and may move in a perpendicular manner with respect to an area of second element 304. Moveable element 302 may also include a mechanically moving element (e.g., an arm, a supporting element, etc.), or moveable element 302 may be part of a flexible material (e.g., a portion of a flexible conducting sheet, etc.). In another embodiment, moveable element 302 is a portion of a comparatively large sheet that is either contiguous or partially separated (e.g., a disk surrounded by an etched gap with supporting elements, etc.). In one embodiment, moveable element 302 has an area of 0.01 μm2 or less. Moveable element 302 may be held away from second element 304 (i.e., opposing a Casimir force) by another non-Casimir force. In one embodiment, a spring force of the material comprising moveable element 302 may also be used to push moveable element 302 and second element 304 apart. In another embodiment, an electromagnetic force may also be induced to push moveable element 302 and second element 304 apart. In another embodiment, the mechanical elastic strain forces of the material of moveable element 302 (or of supporting elements) may be used to maintain a position of moveable element 302.
The interaction of a non-Casimir force and the Casimir force may be taken advantage of such that moveable element 302 may be positioned in at least two stable states (i.e. positions). This interaction of forces may be controlled by the voltage applied to the gate as described above. When applying the voltage to field-effect gate 306, the Casimir force may be controlled by dynamically adjusting Casimir properties of second element 304 or moveable element 302. This may include changing the conductive or insulating properties of second element 304 or moveable element 302. For example, the Casimir force may be switched on or off by altering the conductivity of the semiconductor (e.g., by applying or removing a voltage to field-effect gate 306 such that the semiconductor switches from being non-conductive to conductive, depending on the particular configuration of the gate and semiconductor). When the Casimir force is active and when moveable element 302 and second element 304 are sufficiently close together, the Casimir force can dominate over a non-Casimir force, and moveable element 302 and second element 304 can be pushed together into a first stable position. However, when the Casimir force is inactive, then the non-Casmir force can dominate, and moveable element 302 and second element 304 can be pushed or pulled apart into a second stable position.
Thus, in an embodiment having two stable states, the positioning of moveable element 302 and whether it is in the first or second stable position may be used to implement various transistor devices that control moveable element 302 by varying the Casimir force between moveable element 302 and second element 304. In one embodiment, Casimir-effect device 300 is a switch, and the movement of moveable element 302 acts to open or close an electrical contact of Casimir-effect device 300. In one stable position of moveable element 302, electricity may be allowed to flow through the closed contact. In another stable position of moveable element 302, the contact may be open, such that electricity may not flow therethrough. In another embodiment, Casimir-effect device 300 is an actuator, and the movement of moveable element 302 may perform the mechanical function of the actuator. For example, moveable element 302 may move a component of a microelectromechanical (MEMS) device.
In some embodiments, the interaction of the non-Casimir force and the highly nonlinear Casimir force may allow the device to be stable in either of two states even with a single value of the applied gate voltage. For example, with the Casimir effect active, the position of Casimir-effect device 300 may be stable in a first state with a relatively large first separation between and hold moveable element 302 and second element 304, where the Casimir force on element 302 is small, and may also be stable in a second state with relatively small second separation where the Casimir force on element 302 is large. However, if Casimir-effect device 300 is in the second state, it may be “reset” to the first state, with moveable element 302 in the first position, by deactivating or dynamically adjusting the Casimir force (e.g., by adjusting the conductivity of the semiconductor as described above).
Additional forces may also be utilized to change the position of moveable element 302. In one embodiment, electromagnetic or electrostatic attraction (directed towards or away from second element 304) is utilized. In another embodiment, repulsion from a third surface is utilized. In another embodiment, photon pressure may be utilized to move moveable element 302. In another embodiment, mechanical pressure (e.g., from an atomic force microscopy (AFM) tip or a microelectromechanical (MEMS) actuator, etc.) may be utilized. A bulk force or change in a property may be used to cause a bulk change in the position of multiple moveable elements (e.g., a temperature change). In another embodiment, a non-Casimir force that is holding moveable element 304 may be reduced (e.g., via the application of heat, etc.) so that the Casimir force, when activated, dominates over the non-Casimir force.
In some embodiments, the Casimir force may be used to both “pull in” (move from the first state with relatively greater separation to the second state with relatively lesser separation) a bi-stable device, and to hold the device in the second state. This may be done by using the gate to turn the Casimir effect fully on until moveable element 302 moves towards second element 304 (thereby increasing the Casimir force) and then reducing, but not completely eliminating, the Casimir effect. This may involve either setting the gate voltage to an intermediate value between the voltages associated with two areas of, e.g., element 304, with both areas being turned on (high Casimir force) to “pull in” moveable element 302 and only one being turned on to hold element 302 in the closer position. In the former case, the device may be reset to the first state by setting the gate voltage to the value for minimum Casimir effect; in the latter case, the device may be reset by setting both gates to turn off the Casimir effect.
Referring to
Referring to
In certain embodiments discussed herein, moveable element 302 may be configured to only rest in the first or second stable positions. However, it should be understood that the scope of the present disclosure is not limited to embodiments where moveable element 302 that is only capable of being set in two stable positions. For example, in one embodiment, moveable element 302 may be positioned in one or more stable intermediate positions in addition to the two stable positions discussed above.
Referring to
Referring to
The construction and arrangement of the systems and methods as shown in the various embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the present disclosure.
The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented or modeled using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.
Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.
While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims.
