Abstract
A solid state device and method are described for detecting and using neutrinos. In elementary particle physics there are only three stable particles: the proton, electron and neutrino. The proton and electron have a charge q and are easy to detect, but neutrinos have no charge but a magnetic moment (spin ) and does not strongly interact with matter at room temperature (295 Kelvin). This neutrino detector consists of a semiconducting substrate, with magnetic atoms at the lattice sites. An important feature of this disclosure is that it functions at cryogenic temperatures (0 to 78 K) using the Kondo effect which forms hybrid localized milli-eV band (about 20-4010.sup.3 eV) at the magnetic sits in the semiconductor band gap or conduction band. The neutrinos passing the detector and absorbed at these sites change the resistance of the neutrino detector. In a second embodiment a superconductor is used. The preferred material is a high temperature superconductor (<77 K) such as YBa.sub.2Cu.sub.3O.sub.7-x. The neutrinos dissociate the Cooper pair (electrons) and change the resistance that is measured as in the first embodiment.
Claims
1. A neutrino detector device comprised of: a semiconductor material having magnetic atoms at lattice sites of said semiconductor material; ohmic metal contacts attached to said semiconductor material to measure the change in resistance due to a change in neutrino flux passing through said semiconductor material; a multimeter attached to said metal contacts to measure said change in said resistance; an analog-to-digital (A/D) converter (circuit) attached to said multimeter to convert said change in said resistance to digital storage data for storage on a computer; said neutrino detector is at a temperature below the Kondo transition temperature.
2. The neutrino detector device of claim 1, wherein said semiconductor material is silicon (Si) and said magnetic atoms are iron (Fe).
3. The neutrino detector device of claim 2 wherein said silicon is a single crystal substrate cleaved along the <100> axis and the concentration of said iron (Fe) varies from <0 to 99 atomic percent.
4. The neutrino detector device of claim 1 wherein said magnetic doping atoms are selected from the group comprising Fe, Co, Ni and Pd.
5. The neutrino detector device of claim 3, wherein said single crystal silicon substrates has a high purity of 99.99999 to 99.9999999 for including integrating circuits on the same said silicon substrate.
6. The neutrino detector device of claim 1, wherein said semiconductor material having magnetic atoms at said lattice sites of said semiconductor material has a Kondo transition temperature above the CMBR temperature (3.5 K).
7. A neutrino detector device comprised of: A superconducting material; Ohmic metal contacts attached to said superconducting material to measure the change in resistance due a change in neutrino flux passing through said superconducting material; a multimeter attached across said ohmic metal contacts to measure said change in resistance; said multimeter attached to an analog-to-digital (A/D) circuit to store said change in resistance digitally on a computer; said superconducting material at a temperature below the threshold temperature of said superconducting material.
8. The neutrino detector device of claim 7, wherein said superconductor material are selected from the group that include Lead (Pb) with a transition temperature 7.19 K, Vanadium (V) with a transition temperature 5.03 K, Tantalum (Ta) with a transition (4.48 K).
9. The neutrino detector device of claim 7, wherein said superconductor material are selected from the group that or some compound like V.sub.3Si with a transition temperature 17.1 K, Nb.sub.3Al with a transition temperature 17.5 K and the like which have a critical transition temp. (T.sub.c) above the Cosmos Microwave Background Radiation (CMBR) temperature.
10. The neutrino detector device of claim 7, wherein said superconductor material is a means of propulsion measure a change in resistance due to said neutrino passing through said superconductor.
11. The neutrino detector device of claim 1, herein said Kondo insulator is a means of propulsion when said transition temperature is greater than the CMBR temperature (3.5 K).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 shows a schematic cross section of a neutrino detector composed of a doped semiconductor substrate with magnetic doped sites and a means for measuring a change in resistance.
[0029] FIG. 2 shows the same schematic cross section as the device in FIG. 1 with a neutrino shutter to change or modulate the neutrino flux density.
[0030] FIG. 3 shows a top view of a portion of the neutrino detector with a cross section 3-3 through one of the many magnetic atoms (site) at the semiconductor lattice site.
[0031] FIG. 4 shows a cross section view 3-3 through the magnetic site showing the shallow energy band structure created by the magnetic atom outer shell (d or f shells) in FIG. 3 relative to the semiconductor conduction band vs. distance in the substrate.
[0032] FIG. 5 shows a plot of resistance vs. energy using infrared and Raman spectroscopy frequencies and for temperature at 250 and 20 Kelvin showing the narrow band of about 3510.sup.3 eV due to the Kondo effect in FeSi.
[0033] FIG. 6 shows a cross section of a superconducting neutrino detector which is similar to FIG. 1 but with the magnetically doped semiconductor replaced with a superconductor.
DETAILED DESCRIPTION
[0034] The method for making these neutrino detector devices is now described in more detail with reference to the FIGS. 1-6 listed above. The neutrino device and the instrumentation for measuring and storing the data is described using separate electron equipment, but for single crystal Si substrates the measuring devices can be used to integrated in with the current integrated semiconductor devices on the same silicon substrate.
[0035] Referring first to FIG. 1, a cross sectional view of a neutrino detector is shown composed of a semiconductor substrate 2 with magnetic doped sites 6. The thickness of the substrate is labeled Z. The semiconductor substrate is preferably silicon (Si) and the magnetic sites are preferably iron atoms (Fe). One of the Fe sites is depicted as 6 in FIG. 1. Also depicted is a neutrino flux 4 impinging on the detector 2 from an external source such as from the sun, nuclear reactors, particle accelerators or the Cosmos. One method of forming this Si/Fe alloy is by means of conventional alloying in an induction furnace. However, the preferred method is to deposit Fe using chemical vapor deposition (CVD), or sputter deposition on a Si substrates (wafers) that are currently used in the semiconductor industry. Still another method is to implant Fe into the Si substrate and anneal to activate the Fe at the Si crystalline sites. If semiconductor devices are included on the same substrates, the substrates are preferably cleaved along the <100> crystal orientation and have a very low impurity level 99.9999999 (7/9 or 9/9) are preferred. These silicon substrates are ideal since the neutrino detector can be integrated into the same substrates as the semiconductor devices.
[0036] Also, as shown in FIG. 1 the change in neutrino flux through Fe/Si neutrino detector device 2 can be measured using separate instruments. For example, a multimeter 10 for measuring a change in resistance can be connected across the device using ohmic contacts 8, such as Pt silicide contacts, as is commonly used for silicon integrated circuits.
[0037] The change in resistance is due to a change in neutrino flux 4. The change in resistance can be further analyzed using an analog to digital (A/D) converter 12 and a computer 14 for collecting and storing the neutrino data. However, one can also integrate these electronic circuits on a single chip or substrate with the neutrino detector since the integrated circuits performs very well at very low temperature which is required for the Fe/Si neutrino detector. Although, one can use the 50/50 composition of Fe/Si v phase (see Is FeSi a Kondo insulator, Z. Schlesinger et al in Physica B pages 460-461, published by Elsevvier), the Fe concentration can be varied over a Fe concentration from <0 to 99<. (see CONSTITUION of BINARY ALLOYS by HANSEN 1958 page 713 and pubs by McGraw-Hill). The desired Fe concentration would depend on maximizing the change in resistance do to the neutrino absorption at the Fe sites. Although Fe and Si are preferred, other magnetic impurities, such as Ni, Co and other magnetic elements can be used. Also other materials having the low temperature Kondo effect can be used.
[0038] Referring next to FIG. 2 the neutrino detector 2 of FIG. 1 is shown again but includes a shutter 16 to absorb or modulate some of the neutrinos coming from a source. The shutter 16 can be composed of the material (Si doped with Fe) used for the detector 2. To be effective the shutter is also maintained at the same low temperature as the neutrino detector, about 20 Kelvin.
[0039] Referring now to FIG. 3, a top view of a portion of the Si substrate 2 of FIG. 1 is shown and labeled along the X and Y axis. While the design of the neutrino detector is shown as a portion having a simple rectangular shape, it should be understood that the neutrino detector can take on other various shapes. For example, the detector can take on shapes such as square, round, and the like. Further the neutrino detector can be increased in thickness, as depicted by Z in FIG. 1, or the Fe doped Si substrates 2 can be stacked (not shown) to increase the number of neutrino detection sites. Although Fe and Si are preferred because of the abundance of these elements on earth and elsewhere in the Universe near stars, other Kondo Insulators or semiconductor alloys can be used, such as Ce.sub.3Bi.sub.4Pt.sub.3, CePd.sub.3 and the like.
[0040] Still referring to FIG. 3, a cross section 3-3 through one of the Fe atoms 6 and Si substrate 2. The other Fe atoms (sites) are omitted to simplify the drawing. The Fe nucleus 18 with a radius of about 5.5010.sup.13 cm (centimeter) is at the center of the Fe atom 6 with the atoms outer orbital electrons 20 extending to about 5.5010.sup.8 cm. The outer most Fe atomic electron orbit (d and/or f shells) 20 are responsible for forming a shallow micro-band that merges with the Si band structure.
[0041] Referring next to FIG. 4, the cross-section through 3-3 in FIG. 3 is describe in more detail. In this Fig the horizontal axis X remains the distance in the Si substrate 2. However, and important to this disclosure the vertical axis depicts a simplified energy band structure for Si, measured in electron volts (eV). The Fe atom 6 (FIG. 3 above) forms a shallow band 26 that merges with the Si conduction band 16 (heavy electrons) or with the Si band gap 22 (Kondo effect). This shallow energy band 26 formed by the f or d atomic shells (orbital) 20 of the Fe 6 atom 20 in FIG. 3 forms a shallow localized band 26 (40-6010.sup.3 eV) that is integrated or hybridized with the conduction band 16 in the Si substrate 2.
[0042] Still referring to FIG. 4, and to better understand the function of the neutrino detector 2, a Fermi/Dirac distribution function is shown 21 superimposed over the Si band structure layers 16, 22 and 24 in single crystal silicon, and measured in eV. The energy band labeled 16 is the conduction band, the valence band is labeled 24 and Fermi band gap is labeled 22. When crystals are formed the Paule exclusion principle requires that spin particles do not occupy the same atomic energy levels and therefore form the band structure in solids. The Fermi/Dirac function then shows the distribution of electrons in the solid as a function of temperature. The curve 21 near room temperature (240 K) and the distribution curve 23 near zero degrees Kelvin is shown. At a high temperature, (e.g. 250 K) the portion 21a of the Fermi curve 21 extends into the conduction band 16 and contributes to the conductivity. Also the electrons missing 21b in the valence band 24 contribute positive hole conductivity. The heavy electrons associated with the d and f shell electrons (outer orbital electrons at the Fe sites also contribute to the conductively at higher temperatures. When the temperature of the Fe doped Si substrate 2 is reduced to near zero degrees (0-20 K) the Fermi distribution curve 23 is essentially flat and lies well within the band gap 22. The conduction band 16 is void of electrons and the valence band 24 is filled with electrons. This results in a much lower conductivity a and a higher resistance (receptivity p). The key feature of this device is that at low temperatures the Fe atom's d or f shell electrons are localized at the Fe sites and also do not contribute significantly to the conductivity. At these low temperatures the FeSi neutrino detector is essentially a Kondo insulator.
[0043] Referring next to FIG. 5, the function of the neutrino detector 2 is described in more detail using the Kondo insulator results from the paper cited above by Z. Schlesinger et al. titled, Is FeSi a Kondo Insulator. Schlesinger's FIG. 1a, page 461 is repeated here for expediency in FIG. 5. This disclosure utilizes this Kondo effect to capture low energy neutrinos to change the conductivity a of the neutrino detector 2.
[0044] As shown in FIG. 5 (FIG. 1a of the reference sited above), the vertical axis is the change in the conductivity of FeSi alloy (in reciprocal ohms-cm) as a function of the energy along the horizontal axis as measured in frequency 2 (cm.sup.1), where the frequency in the electromagnetic (HE) energy and is related to the Plank's equation by E=h.
[0045] The reference sited above for the Kondo study is a 50/50 atomic percent composition. However, for the purpose of this disclosure the neutrino detector would vary over the composition range from about 1 to 99% for Fe in Si. One can employ a variety of techniques to optimize the properties of the neutrino detector. For example one can use microwave, infrared, Raman absorption spectroscopy techniques to study and optimize the low temperature electronic properties of the detector. Also FeSi is the preferred material because it is compatible with the current day integrated circuit industry.
[0046] As shown in FIG. 5, at room temperature (250 K), the conductivity, curve 28, does not change significantly as a function of energy in (at microwave and infrared freq.). Typically, as the temperature decreases the resistivity of semiconductor increases slowly as described above, unlike conductors (metals) that decreases in resistivity because of lattice vibration (phonons). A key feature at these high temperatures is that the resistivety is essentially constant even at very low energy in the millevolt range. Therefore, neutrinos absorbed at the magnet atom sites would not significantly change the resistivity in the detector.
[0047] Now referring to curve 30 in FIG. 5, as the temperature of the neutrino detector 2 (in FIG. 4) is reduced below Kondo transition temperature T.sub.k the Kondo semiconductor resistivity rapidly increases and becomes a Kondo insulator. More specially, as shown for the FeSi neutrino detector 2 as the temperature is lowered to a near 0 Kelvin (20 K) the conductivity approach zero, curve 30, and is similar to most Kondo insulators. The conductive of the detector 2 increases when low energy neutrinos pass through the Fe site and interact with the heavy electrons in the shallow Kondo band 26 (in FIG. 4). The electron mass does not change but in the Fe field (F=MA) appear to be more massive. The F is the modified force from the Fe field.
[0048] Referring next to FIG. 6, a second embodiment is shown for a neutrino detector. In this embodiment a superconductor material 18 is used to replace the Kondo semiconductor 2, as shown in FIG. 1. For example a high temperature (<78 K) superconductor such as Yttrium Barium Copper Oxide (YBa.sub.2Cu.sub.3O.sub.7-x) 18 or the like can be used. However, other more conventional low temperature superconductors can also be used that have a transition temperature above the Cosmic Microwave (CMBR) temperatures (3.5 K), such as V.sub.3Si at a temp. <17.1 K, Nb.sub.3Sn and the like with temperatures >than 3.5 K.
[0049] Also as described above the superconducting neutrino detector 18 can be monitored using a resistance meter (multimeter) 10 and using an analog-to-digital (A/D) converter and stored on a computer.
[0050] This lower temperature superconductor would be practical in outer space. Further, since Si semiconducting integrated circuits function well at low temperatures, a number of these conventional low temperature superconductors can be integrated on the same Si substrates. In this type of neutrino detect a reduction in Cooper pairs 32 would increase the conventional current.
[0051] This would result in an increase in resistance when the neutrino detector is in the superconducting state and the neutrino flux increases. The neutrino energy absorbed by the detector would be perceived as also having a change in gravity field.
[0052] While the disclosure has been particularly shown and described with reference to the preferred embodiments for detecting neutrinos thereof, it will be understood by one skilled in the art that various changes in form and details may be made without departing from spirit and scope of the disclosure. For example, although Fe.sub.xSi.sub.y is the preferred alloy and single crystal, other Kondo semiconductors that turn to Kondo insulators can be used near or below the Kondo transition temperature T.sub.k. Also, in the second embodiment high temperature superconductors are used. However, superconductors at lower temperatures can also be used that have a transition temperature above the CMBR temperature for used in outer space.
