The present disclosure relates generally to semiconductors, and more specifically to energy storage and diode semiconductor devices.
Silicon is typically used to make semiconductor devices by doping with excess electrons (n-type) or holes (p-type). Diodes are semiconductor devices made by forming a junction between p-type and n-type materials. Such devices are bipolar, and can be forward or reverse biased by applying a voltage across the junction.
Capacitors are traditionally made with conductive plates separated by a dielectric material, such as silicon dioxide. These plates act as a positive node (anode) and a negative note (cathode). The plates can also be arranged in an alternating “stacked” configuration to boost the capacitance of the capacitor. Capacitance is also created by a diode p-n junction when the diode is biased, and a depletion region develops over the border between the n-type and p-type doped materials of a junction diode. The width of the depletion region is adjustable by application of a variable reverse-biased voltage across the diode terminals. The depletion region width determines a capacitance across the diode.
In one embodiment, a charge storage device can include: a first node having a plurality of n-type diamond layers connected together; and a second node having a plurality of p-type diamond layers connected together, the plurality of p-type diamond layers being interleaved with the plurality of n-type diamond layers, where each of the plurality of diamond layers is formed using chemical vapor deposition (CVD).
In one embodiment, a method of forming a charge storage device can include: forming a first node portion from n-type diamond material using CVD; forming a second node portion from p-type diamond material using CVD; and repeating the forming the first node portion and the forming the second node portion for each of a plurality of layers, wherein the plurality of layers are interleaved between the p-type and n-type diamond material.
In one embodiment, an apparatus can include: an n-type diamond layer having a plurality of n-doped carbon atoms; a p-type diamond layer having a plurality of p-doped carbon atoms, where each layer has a thickness in a range of from about an atom spacing to greater than about 1 nm; an n-lead coupled to the n-type diamond layer, and where each of the diamond layers is formed using CVD; and a p-lead coupled to the p-type diamond layer, where the layers conform to a predetermined shape.
Particular embodiments include a capacitor or diode formed of layered diamond, with layers alternatively doped n-type and p-type. In some cases, one or more of the layers may be non-doped or intrinsic, and maybe used to form a capacitor structure. For example, a non-doped intrinsic crystalline diamond layer may be used as a dielectric between alternatively doped n-type and p-type layers. Thus, particular embodiments include: (i) the formation of junction diode/capacitor devices having n-doped and p-doped interleaved diamond layers; and/or (ii) the formation of capacitor structures having interleaved n-doped diamond, dielectric, and p-doped layers.
The diamond can be assembled in multiple layers by any suitable processing technique, such as chemical vapor deposition (CVD). For example, a form of carbon can be used as a feedstock in a CVD process for application of diamond layers. The CVD allows atoms to achieve an appropriate arrangement for crystalline pattern formation. Resultant structures as described herein can include a capacitor for electrostatic energy storage, a diode (e.g., a light-emitting diode (LED)), a battery, etc., and may be suitable for use in various electronic products.
Particular embodiments can include diamond portions layered in a “sandwich” or “stacked sandwich” configuration so as to afford as large a p-n junction as possible. The capacitance associated with such a p-n junction when the junction is biased (either forward or reversed) results in a repository for electrostatic charge. Further, this capacitance is variable (e.g., when in a variable capacitor or varactor diode configuration) due to biasing that affects depletion region length or distance.
For example, in sandwich parallel plate capacitor configurations with dielectrics, capacitance may be determined as shown below in Equation 1:
C=ε
k
A/d=κ
eε0A/d (1)
In Equation 1, C=capacitance, A=cross-sectional area of the capacitor, d=distance across the dielectric, ε0=the permittivity of free space=8.85×10−12 F/m, εk=the permittivity of the dielectric, and κe=the dielectric constant of the dielectric.
In order to make capacitors with smaller dimensions and higher capacitances using the same or similar materials, e.g., anodes and cathodes may be “stacked” to form a “sandwich” capacitors structure, thereby increasing an effective area (A) and raising an overall capacitance value. Of course, other suitable structures, some examples of which will be discussed below, can also be supported in particular embodiments.
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Layer thicknesses in particular embodiments can range from as low as an atom spacing, as well as from about 0.3 nm to about 3 nm, such as from about 0.75 nm to about 1.5 nm, and including about 1 nm. Further, different structures, such as prismatic shapes, cylinders, queues, etc. can be formed by combining any number of layers or slices as described herein. For example, 70 million layers can be used to form an object with a length of about 7 cm, but any number of layers can be employed in particular embodiments.
Chemical vapor deposition (CVD) can be used for deposition of very thin wafers of diamond-crystal carbon. In addition, by doping with, e.g., boron (B) or phosphorus (P), both positive (p-type) and negative (n-type) semiconductor materials can be developed. For example, using pure or intrinsic diamond crystal as a dielectric layer, and p-type and n-type doped diamond crystal as anode and cathode terminals, sandwich capacitor structures can be formed. In addition, any other suitable dopants, such as nitrogen for n-type dopants, can be used in particular embodiments.
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Alternatively, n-doped anode and p-doped cathode portions can be placed in contact with each other, and without an intervening dielectric layer. Such a structure forms a p-n junction that may function as a diode, or a capacitor with varying capacitance values across a depletion layer at the junction, and based on an applied bias across the anode and cathode terminals. The process of steps 206, 210, and alternately 208, can be repeated until a final layer (212) of the stacked sandwich capacitor structure is formed, thus completing the flow (214).
CVD of diamond can be used to produce cultured diamond by creating an atmosphere for carbon atoms in a gas to settle on a substrate in crystalline form. CVD diamond growth can occur under low pressure (e.g., 1-27 kPa; 0.145-3.926 psi; 7.5-203 Torr), and may involve feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. These gases include a carbon source, and may include hydrogen as well. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source can be used to generate a plasma in which the chamber gases are broken down such that complex chemistries occur.
Such CVD diamond growth can allow growth of diamond over large areas, growth of diamond on a substrate, and control over properties of the diamond produced. Growing diamond directly on a substrate allows addition of many of diamond's important qualities to other materials. For example, because diamond has the highest thermal conductivity of any material, layering diamond onto high heat producing electronics (e.g., optics, transistors, etc.) allows the diamond to be used as a heat sink. Characteristics of diamond include very high scratch resistance and thermal conductivity, combined with a lower coefficient of thermal expansion than, e.g., Pyrex glass, a coefficient of friction close to that of, e.g., Teflon (Polytetrafluoroethylene), and strong lipophilicity.
In addition, CVD diamond growth affords control of properties of the diamond produced. As used in the area of diamond growth, “diamond” can include any material having suitably bonded carbon atoms. By regulating the processing parameters (e.g., the gases introduced, pressure the system is operating under, temperature of the diamond, method of generating plasma, etc.), many different “diamond” or diamond like materials. Further, single crystal diamond can be made containing various dopants, and polycrystalline diamond having grain sizes from under about 1 nm (e.g., an atom spacing, spacing of a few atoms, etc.) to about several micrometers can be grown.
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When such a stacked p-n-neutral junction structure is formed as described herein, a semiconducting capacitor with relatively good thermal and electrical properties can be achieved. For example, by using diamond materials, an electrostatic energy storage device is limited by the dielectric strength or breakdown voltage E=2×109 V/m for diamond (about the highest known for any material), giving a maximum electric storage density of 1.0×108 J/m3.
In one parallel plate example, a layer thickness (e.g., anode, cathode, dielectric) can be about 50 μm. If roughly the dimensions of a car battery (e.g., about 8″×8″×12″), and since two of every four “slices” is dielectric material, and one of every four is p-doped, and one of every four is n-doped, that means one “segment” of the battery is about 200 μm, and the cross-sectional area is 2×8″×12″=192 in.2 In a battery that is 8 inches tall, about 8″/200 μm, or about 200 k, segments are contained therein. The capacitance for one such segment is given as shown below in Equation 2.
C=ε
k
A/d=(5.04×10−11 F/m)×(0.124 m2)÷(5×10−5 m). (2)
Thus, C=1.25×10−7 F, or 125 nF. The electric field in the segment when charged to 24 VDC=24 V/50 μm=480,000 V/m. The energy in one segment at 24 VDC=½ CV2=½ (1.25×10−7)(24)2=3.6×10−5 J.
Diamond also has mechanical properties that make it feasible to create many ultra-thin layers, and still have a robust product. For example, LEDs, as well as usage in watches and jewelry and so forth, can be formed in particular embodiments. In addition, “energy storage” applications can include batteries for cell phones, cameras, cars, pacemakers, diesel electric locomotives, power plants, and so on. Thus, particular embodiments are suitable for a very wide range of applications and sizes of storage devices. For example, particular embodiments can be used to form energy storage devices with substantially long lives, making them useful for pacemakers, etc., as well as other battery applications. For jewelry applications, a gem could essentially be the battery itself. In LED and battery applications, a gem-like LED can “twinkle.”
When making electrostatic storage devices from diamond via a CVD process, the maximum field strength (and consequently, breakdown voltage) can be made large enough for any potential application. To accomplish this, the “sandwich” or interleaved layer approach with doped diamond, pure diamond, and/or reverse-biasing the capacitor or diode-capacitor (resulting in a “zener effect” if reverse-biased), can be used.
The maximum field that could be stored in a capacitor may be determined by the dielectric strength or breakdown voltage (e.g., E=2×109 V/m for diamond, which is about the highest known for any material), giving a maximum electric storage density of 1.0×108 joules/m3. However, reverse-biased doped diamond (p/n) junction and “sandwich” materials (e.g., p-neutral-n) may yield much higher breakdown voltages. In maximizing both the dielectric coefficient and the breakdown voltage to achieve maximum possible energy density (joules/cm3), various sandwich combinations (e.g., p-n-p-n- . . . , or p-neut-n-neut-p, or p-neut-p-neut- . . . , or n-neut-n-neut- . . . , etc.) as well as the source voltage polarity, can be accommodated.
Although particular example structures described herein show a simple p-n-p-n- . . . and a simple p-neut-n-neut-p- . . . configuration, any other suitable configuration or permutation can be utilized in particular embodiments. These various configurations represent example interleaved layer variations in accordance with certain embodiments. Table 1 below shows various examples of such interleaving variations, where “p”=positively doped carbon, “n”=negatively doped carbon, and “neut”=non-doped carbon).
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Although the description has been described with respect to particular embodiments thereof, these particular embodiments are merely illustrative, and not restrictive. For example, any semiconductor device formed using doped diamond layers, as well as possibly intrinsic diamond layers, can be utilized in particular embodiments.
Any suitable programming language can be used to implement the routines of particular embodiments including C, C++, Java, assembly language, etc. Different programming techniques can be employed such as procedural or object oriented. The routines can execute on a single processing device or multiple processors. Although the steps, operations, or computations may be presented in a specific order, this order may be changed in different particular embodiments. In some particular embodiments, multiple steps shown as sequential in this specification can be performed at the same time.
Particular embodiments may be implemented in a computer-readable storage medium for use by or in connection with the instruction execution system, apparatus, system, or device. Particular embodiments can be implemented in the form of control logic in software or hardware or a combination of both. The control logic, when executed by one or more processors, may be operable to perform that which is described in particular embodiments.
Particular embodiments may be implemented by using a programmed general purpose digital computer, by using application specific integrated circuits, programmable logic devices, field programmable gate arrays, optical, chemical, biological, quantum or nanoengineered systems, components and mechanisms may be used. In general, the functions of particular embodiments can be achieved by any means as is known in the art. Distributed, networked systems, components, and/or circuits can be used. Communication, or transfer, of data may be wired, wireless, or by any other means.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. It is also within the spirit and scope to implement a program or code that can be stored in a machine-readable medium to permit a computer to perform any of the methods described above.
As used in the description herein and throughout the claims that follow, “a”, “an”, and “the” includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
Thus, while particular embodiments have been described herein, latitudes of modification, various changes, and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of particular embodiments will be employed without a corresponding use of other features without departing from the scope and spirit as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit.