Patent Publication Number: US-2022238726-A1

Title: Quantum diode for transforming an alternating current, in particular high frequency alternating current, into a direct current

Description:
The present invention refers to a quantumdiode for transforming an alternating current, in particular a high frequency alternating current, into a direct current. 
     Particularly, the invention relates to the structure of said quantum diode configured to allow said diode to operate up to the frequencies belonging to the THz band and to have a high switching speed. 
     The operation of said quantum diode is based on the movement of a quantity of electrons which by tunnel effect moves from a first electrode to a second electrode of said quantum diode, jumping an electrically insulating layer. 
     PRIOR ART 
     Currently, they are known diodes for transforming an alternating current into a direct current. 
     An example of a diode for rectifying an alternating current into a direct current is the Schottky diode which includes a metal—semiconductor junction. 
     A disadvantage of said diode is that said junction implies that the electrons physically cross a dielectric layer, so that a quantity of energy is absorbed by the junction itself, with a consequent heating of the diode itself. 
     However, the Schottky diode is not a quantum diode. 
     A first example of quantum diode is a MIM diode, i.e. a metal-insulating-metal type diode. 
     A disadvantage of this MIM diode is due to the complexity of the structure and to the difficulty of production. 
     A second example of a quantum diode is a MIIM diode, i.e. a metal-insulating-insulating-metal type diode. 
     A disadvantage of this MIIM diode is that a greater polarization than the MIM diode is necessary to allow the electrons to jump over two insulating layers. 
     Consequently, a power supply unit is required. 
     Like the MIM diode, a further disadvantage is due to the complexity of the structure and to the difficulty of production. 
     AIM OF THE INVENTION 
     Aim of the present invention is to overcome said disadvantages by providing a quantum diode to transform an alternating current, in particular a high frequency alternating current, into a direct current, capable of operating up to frequencies of the THz band and having a high switching capacity. 
     In fact, the structure of the quantum diode, object of the invention, is designed to allow the quantum diode itself to transform an alternating current with a frequency in the THz band into a direct current. 
     A second aim of the present invention is to provide a quantum diode having a simple structure and a low production cost. 
     A further aim of the present invention is to provide a quantum diode which does not heat up and has a higher efficiency than a junction diode, since said quantum diode dissipates a quantity of heat and an irrelevant amount of energy with respect to said junction diode. 
     OBJECT OF THE INVENTION 
     It is therefore object of the invention a quantum diode for transforming an alternating current, in particular a high frequency alternating current, into a direct current, comprising:
         a first conductive metal layer, where said first conductive metal layer behaves as a first electrode or cathode of said quantum diode and comprises a first surface and a second surface, opposite to the first surface, a third surface joining said first surface and said second surface, where said third surface contacts said first surface at a first contact line in such a way that said third surface and said first surface form a first angle greater than or equal to 90° and less than 180°,   an electrically insulating layer having a first end and a second end and comprising a first portion and a second portion,   where   said first portion at least partially contacts said third surface of said first conductive metal layer and is parallel to said third surface, and said second portion contacts a portion of the first surface of said first conductive metal layer and is parallel to said portion of said first surface,   said first portion and said second portion are arranged so as to form an angle equal to said first angle,   a second conductive metal layer having a first end and a second end and comprising a first portion and a second portion,   where   said first portion contacts the first portion of said electrically insulating layer and is parallel to said first portion, and   said second portion at least partially contacts the second portion of said electrically insulating layer and is parallel to said second portion,   said first portion and said second portion are arranged so as to form an angle equal to said first angle,   a third conductive metal layer behaving as a second electrode or anode, where said third conductive metal layer at least partially contacts the first portion and the second portion of said second conductive metal layer and is electrically isolated from said first conductive metal layer.       

     In particular, said first conductive metal layer is made of a first metallic material, said second conductive metal layer is made of a second metal material, different from said first metallic material, and said first conductive metal layer and said second conductive metal layer are separated by said electrically insulating layer and the thickness of said electrically insulating layer is between 1.5 nm and 5 nm, so that, when in use, a quantity of electrons moves from said first conductive metal layer to said second conductive metal layer, jumping, by tunnel effect, said electrically insulating layer at said first contact line. 
     With reference to the first conductive metal layer, said first conductive metal layer can be made of gold. 
     With reference to the second conductive metal layer, said second conductive metal layer can be made of chrome. 
     Furthermore, said first conductive metal layer and said third conductive metal layer can be made of the same metallic material. 
     It is preferable that said first conductive metal layer has a thickness greater than the thickness of said second conductive metal layer. 
     In particular, said first conductive metal layer can have a thickness between 50 nm and 100 nm, preferably 50 nm. 
     Said second conductive metal layer can have a thickness between 10 nm and 30 nm, preferably 10 nm. 
     Furthermore, said third conductive metal layer can have a thickness between 50 nm and 100 nm, preferably 50 nm. 
     With reference to the electrically insulating layer, said electrically insulating layer can be made of dialuminium trioxide or hafnium dioxide or gallium. 
     Said third conductive metal layer can comprise a first portion and a second portion. 
     The first portion of said third conductive metal layer at least partially contacts the first portion of said second conductive metal layer and is parallel to the latter, and the second portion of said third conductive metal layer at least partially contacts the second portion of said second conductive metal layer and is parallel to to the latter. The first portion and the second portion are arranged so as to form an angle equal to said first angle. 
     In a first alternative, said quantum diode can comprise a dielectric layer comprising a first surface, and said first conductive metal layer is arranged on a portion of said first surface of said first dielectric layer. Furthermore, the first end of said electrically insulating layer, the first end of said second conductive metal layer and a portion of said third conductive metal layer can contact said first surface of said dielectric layer. 
     In a second alternative, said quantum diode can comprise a dielectric layer comprising a first surface, and a further conductive metal layer, arranged between said first conductive metal layer and said dielectric layer, where said further metal layer is made of a further metallic material, different from the first metallic material of said first conductive metal layer. Furthermore, said further conductive metal layer comprises a first surface and a second surface, opposite to said first surface. The first surface of said further conductive metal layer can contact at least a portion of said second surface of the first conductive metal layer, as well as the first end of said electrically insulating layer, the first end of said second conductive metal layer and a portion of the third conductive metal layer. The second surface at least partially can contact the first surface of said dielectric layer. 
     It is preferable that said further conductive metal layer is made of chrome. 
     Furthermore, said further conductive metal layer can have a thickness between 10 nm and 30 nm, preferably 10 nm. 
    
    
     
       FIGURE LIST 
       The present invention will be now described, for illustrative, but not limitative purposes, according to its embodiment, making particular reference to the enclosed figures, wherein: 
         FIG. 1  is a schematic cross-sectional view of the quantum diode, object of the invention; 
         FIG. 2  is an exploded schematic view of the quantum diode of  FIG. 1 ; 
         FIG. 3  is a schematic view showing only some layers of the quantum diode. 
     
    
    
     DETAILED DESCRIPTION 
     Everywhere in this description and in the claims the case where the term “comprises” is replaced by the term “consists of” is included. 
     With reference to the  FIGS. 1-3 , a quantum diode for transforming an alternating current, in particular a high frequency alternating current, into a direct current. 
     Said quantum diode comprises:
         a first conductive metal layer  1 , where said first conductive metal layer  1  behaves as a first electrode or cathode of said quantum and comprises a first surface  1 A, a second surface  1 B, opposite to the first surface  1 A, and a third surface  10  (arranged between said first surface  1 A and said second surface  1 B) joining said first surface  1 A and said second surface  1 B, where said third surface  10  contacts said first surface  1 A at a first contact line L 1  in such a way that said first surface  1 A and said third surface  10  form (each other) a first angle α greater or equal to 90° and less than 180°,   an electrically insulating layer  7  having a first end and a second end and comprising:
           a first portion  71 , and   a second portion  72 ,   where   said first portion  71  at least partially contacts said third surface  1 C of said first conductive metal layer  1  and is parallel to said third surface  10 , and   said second portion  72  contacts a portion of the first surface  1 A of said first conductive metal layer  1  and is parallel to said portion of said first surface  1 A,   
           a second conductive metal layer  2  having a first end and a second end and comprising:
           a first portion  21 , and   a second portion  22 ,   where   said first portion  21  at least partially contacts the first portion  71  of said electrically insulating layer  7  and is parallel to said first portion  71 , and   said second portion  22  at least partially contacts the second portion  72  of said electrically insulating layer  7  and is parallel to said second portion  72 ,   
           a third conductive metal layer  3  behaving as a second electrode or anode, where said third conductive metal layer  3  at least partially contacts the first portion  21  and the second portion  22  of said second conductive metal layer  2  and is electrically isolated from said first conductive metal layer  1  (by means of said electrically insulating layer  7 ).       

     With reference to the first conductive metal layer  1  and to the second conductive metal layer  2 , each of said layers is made of a respective metal material. 
     In particular, said first conductive metal layer  1  is made of a first metal material and said second conductive metal layer  2  is made of a second metal material, different from said first metal material. 
     The fact that the metallic material with which the first conductive metal layer  1  is made is different from the metal material with which the second conductive metal layer  2  is made implies an “asymmetry” in the structure of the quantum diode allowing the quantum diode to rectify at high speed the alternating current in a direct current. 
     Furthermore, said first conductive metal layer  1  and said second conductive metal layer  2  are separated from said electrically insulating layer  7  and the thickness of said electrically insulating layer  7  is between 1.5 nm and 5 nm (preferable 2 nm, as said below). 
     The fact that the thickness of said electrically insulating layer  7  is so reduced facilitates the jump of electrons from the first conductive metallic layer  1  to the second conductive metallic layer  2 , preventing the electrons, having reached the second conductive metallic layer  2 , from returning to the first metallic layer conductor  1 . 
     The thickness dimensions of the electrically insulating layer  7  above mentioned, on the one hand, avoid the risk of short circuit between the first conductive metallic layer  1  and the second conductive metallic layer  2  and, on the other side, ensure that the electrons reach the second layer metallic conductor  2 . 
     In fact, said quantum diode is configured to transform an alternating current into a direct current through a jump of electrons from the first conductive metal layer  1  to the second conductive metal layer  2 , by tunnel effect, at said first contact line L 1 , so that the electrically insulating layer  7  (arranged between said first conductive metal layer  1  and said second conductive metal layer  2 ) is jumped by said electrons. 
     In fact, when the quantum diode is in use, a quantity of electrons moves from the first conductive metal layer  1  to the second conductive metal layer  2 , jumping, by tunnel effect, the electrically insulating layer  7  at the first contact line L 1 . 
     With reference to the first conductive metal layer  1 , the third surface  1 C contacts said second surface  1 B at a further first contact line L 1 ′. 
     Furthermore, said first conductive metal layer  1  comprises a fourth surface  1 D (arranged between said first surface  1 A and said second surface  1 B), facing said third surface  1 C, which joins said first surface  1 A and said second surface  1 B, where said fourth surface  1 D contacts said first surface  1 A at a second contact line L 2  in such a way that said first surface  1 A and said fourth surface  1 D form (each other) a second angle β greater than or equal to 90° and less than 180°. 
     In fact, said fourth surface  1 D and said first surface  1 A are arranged in such a way as to form said second angle β which, in the embodiment being described, is equal to the first angle α. 
     Said fourth surface  1 D contacts not only said first surface  1 A but also said second surface  1 B. 
     In particular, said fourth  1 D contacts said second surface  1 B at a further second contact line L 2 ′. 
     With reference to the cross section of the first conductive metal layer  1 , said first conductive metal layer  1  has a first height H 1 . 
     Furthermore, in cross-section, said first conductive metal layer  1  has the shape of an isosceles trapezoid. 
     With reference to the second conductive metal layer  2 , the first portion  21  and the second portion  22  are arranged in such a way as to form an angle equal to said first angle α. 
     In cross section said second conductive metal layer  2  has a second height H 2 , less than said first height H 1 . 
     In other words, the thickness of the first conductive metal layer  1  is greater than the thickness of the second conductive metal layer  2 . 
     So, with reference to the structure of the quantum diode, the fact that the first conductive metal layer  1  and the second conductive metal layer  2  have different thicknesses (i.e. different heights) contributes to the “asymmetry” of the structure of the quantum diode allowing the quantum diode to rectify the alternating current into a direct current at a higher speed. 
     The thickness of the first conductive metal layer  1  can be between 50 nm and 100 nm, preferably 50 nm. 
     The thickness of the second conductive metal layer  2  can be between 10 nm and 30 nm, preferably 10 nm. 
     In the embodiment being described, the first metal conductive layer is preferable made of gold. 
     In particular, the first conductive metal layer  1  and the third conductive metal layer  3  are made of the same metal material, preferable gold. 
     In the embodiment being described, the third metal conductive layer  3 , seen in cross section, has the same height as the first conductive metal layer  1 . 
     In other words, said first conductive metal layer  1  and said third conductive metal layer  3  has the same thickness. 
     Therefore also the thickness of the third conductive metal layer  3  can be between 50 nm and 100 nm, preferably 50 nm. 
     In the embodiment being described, said second conductive metal layer  2  is preferably made of chromium. 
     With reference to the electrically insulating layer  7 , the first portion  71  and the second portion  72  are arranged in such a way as to form an angle equal to said first angle α. 
     In particular, said electrically insulating layer  7  is preferable made of dialuminium trioxide (Al 2 O 3 ). 
     The thickness of said electrically insulating layer  7  is less than the thickness of the second conductive metal layer  2 . 
     As already said, in fact, the thickness of said electrically insulating layer  7  can be between 1.5 nm e 5 nm, preferable 2 nm. 
     Alternatively, said electrically insulating layer  7  can be made of hafnium dioxide (HfO 2 ) or gallium (Ga), without thereby departing from the scope of the invention 
     With reference to the third conductive metal layer  3 , said third conductive metal layer  3  has a first end and a second end and comprises:
         a first portion  31 ,   a second portion  32 .       

     Said first portion  31  at least partially contacts the first portion  21  of the second conductive metal layer  2  and is parallel to said first portion  21  and said second portion  32  at least partially contacts the second portion  22  of the second conductive metal layer  2  and is parallel to said second portion  22 . 
     The first portion  31  and the second portion  32  of the third conductive metal layer  3  are arranged in such a way as to form an angle equal to said first angle α. 
     Furthermore, in the embodiment being described, said quantum diode comprises a fourth conductive metal layer  4  and a fifth conductive metal layer  5   
     However, said fourth conductive metal layer  4  and said fifth conductive metal layer  5  are not necessary. 
     With reference to the fourth conductive metal layer  4 , said fourth conductive metal layer  4  has a first end and a second end and comprises:
         a first portion  41 , and   a second portion  42 .       

     Said first portion  41  at least partially contacts the fourth surface  1 D of the first conductive metal layer  1  and is parallel to said fourth surface  1 D. 
     Said second portion  42  at least partially contacts a further portion of the first surface  1 A of said first conductive metal layer  1  and is parallel to said further portion (where said further portion of the first surface  1 A is different from the portion of the first surface  1 A being in contact with the second portion  72  of the electrically insulating layer  7 ) 
     The fifth conductive metal layer  5  at least partially contacts both said first portion  41  and said second portion  42  of said fourth conductive metallic layer  4 . 
     With reference to the quantum diode, as already said, the fourth surface  1 D of the first conductive metal layer  1  contacts the first surface  1 A belonging to the same first conductive metal layer  1 , at said second contact line L 2  in such a way that said fourth surface  1 D and a said first surface  1 A form (each other) a second angle β greater than 90° and less than 180°. 
     Furthermore, the first portion  41  of the fourth conductive metal layer  4  and the second portion  42  of the same fourth conductive metal layer  4  are arranged in such a way as to form an angle equal to said second angle  3 . 
     With reference to the fifth conductive metal layer  5 , as shown in the Figures, said fifth conductive metal layer  5  is at a predetermined distance from the third conductive metal layer  3  to avoid the short circuit between said conductive metal layers. Consequently, the third conductive metal layer  3  and the fifth conductive metal layer  5  are not in contact with each other. 
     In particular, the fifth conductive metal layer  5  comprises:
         a first portion  51  contacting at least partially the first portion  41  of the fourth conductive metal layer  4  and is parallel to said first portion  41 ,   a second portion  52  contacting at least partially the second portion  42  of said fourth conductive metal layer  4  and is parallel to said second portion  42 .       

     The first portion  51  and the second portion  52  are arranged between in such a way as to form an angle equal to said second angle  3 . 
     In the embodiment being described, said second conductive metal layer  2  and said fourth conductive metal layer  4  have the same thickness and are made of the same metal material, preferable chrome. 
     Furthermore, the second portion  72  of the electrically insulating layer  7  and the second portion  42  of the fourth conductive metal layer  4  are substantially coplanar. 
     In the embodiment being described, said quantum diode diode comprises:
         a dielectric layer  8  comprising a first surface  8 A,   a further conductive metal layer  6 , arranged between said first conductive metal layer  1  and said dielectric layer  8         

     With reference to the dielectric layer, said dielectric layer  8  serve as “thermal plane” (capable of collecting thermal energy) and has a thickness based on the frequency of the alternating current to be transformed into direct current. 
     In particular, said dielectric layer  8  also comprises a second surface  8 B, opposite to said first surface  8 A. 
     With reference to the further conductive metal layer  6 , said further conductive metal layer  6  comprises a first surface  6 A and a second surface  6 B, opposite to said first surface  6 A. 
     Said first surface  6 A at least partially contacts a portion of the second surface  1 B of the first conductive metal layer  1 , as well as the first end of the first portion  71  of said electrically insulating layer  7 , the first end of the first portion  21  of said second conductive metal layer  2  and a portion of the third conductive metal layer  3 . 
     Furthermore, in the embodiment being described, said first surface  6 A also contacts the first end of the first portion  41  of the fourth conductive metal layer  4  and a portion of the fifth conductive layer  5 . 
     Said second surface  6 B at least partially contacts the first surface  8 A of said dielectric layer  8 . 
     In the embodiment being described, said further conductive metal layer  6  is made of a further metal material, different from the first metal material of the first conductive metal layer  1 , so as to contribute to the “asymmetry” of the structure of the quantum diode. 
     In particular, in the embodiment being described, said further conductive metal layer  6  is made of chrome. 
     However, said further conductive metal layer  6  is not necessary. 
     In fact, on the basis of the metallic material that is chosen to make the first conductive metallic layer  1 , it is not necessary for the quantum diode to comprise in addition to the dielectric layer  8  also said further conductive metallic layer  6 . 
     Hence, in a variant of the quantum diode in which said further conductive metallic layer  6  is not present, the first conductive metallic layer  1  is arranged directly on a portion of the first surface  8 A of the dielectric layer  8 . 
     In this variant, the first end of the first portion  71  of the electrically insulating layer  7 , the first end of the first portion  21  of said second conductive metallic layer  2  and a portion of said third conductive metallic layer  3  contact the first surface  8 A of the dielectric layer  8 . 
     Furthermore, the first end of the first portion  41  of the fourth conductive metal layer  4  and a portion of the fifth conductive metal layer  5  contact the first surface  8 A of said dielectric layer  8 . 
     Either in the case where the quantum diode comprises the dielectric layer  8  and the further conductive metal layer  6  or only the dielectric layer  8  (without therefore the need for the further conductive metal layer  6  to be present in the structure of the quantum diode), said dielectric layer  8  is made of silicon dioxide (SiO 2 ) and has a thickness of between 50 nm and 300 nm, preferably 300 nm, based on the frequency of the alternating current to be transformed into direct current. 
     Said further conductive metal layer  6  can have a thickness between 10 nm and 30 nm, preferably 10 nm. 
     The thickness dimensions of the further conductive metallic layer  6  allow said further conductive metallic layer  6  to function as a reinforcement layer for the first conductive metallic layer  1  and allow the first conductive metallic layer  1  to have greater stability with respect to the dielectric layer  8 . 
     Furthermore, the quantum diode comprises a support layer  9 . 
     Said support layer  9  comprises a first surface  9 A, arranged in contact with the second surface  8 B of the dielectric layer  8 . 
     Said support layer  9  is made of a material selected from the following group: ceramic, polycarbonate, polyethylene, polyester fabric, cycloolefin copolymers, preferably Topas. 
     Finally, the fact that the portions of different layers in contact with each other are parallel reduces the dispersion of electrons. 
     ADVANTAGES 
     Advantageously, as already mentioned, the quantum diode, object of the invention, allows to transform an alternating current (in particular a high frequency alternating current) in a direct current, where said alternating current can be generated for example by an electromagnetic wave picked up by an antenna to which said quantum diode is connected. 
     A second advantage is given by the fact that said quantum diode is capable of operating also at frequencies in the THz band. 
     A third advantage is given by the fact that said quantum diode has a high switching speed which allows the quantum diode itself to be used in different electronic devices/systems, for example in an antenna configured to resonate with the electromagnetic waves picked up by said antenna or in optical devices/systems configured to work in the infrared or in transmission devices/systems to transmit data at high speed, for civil or military use, or in a computer to encode information. 
     A fourth advantage is given by the fact that said quantum diode produces a greater quantity of energy compared to a junction diode since the quantity of electrons dispersed after jumping the electrically insulating layer is limited. 
     A further advantage is given by the fact that said quantum diode does not heat up and dissipate in terms of heat and energy irrelevant quantities compared to a junction diode. 
     The present invention has been described for illustrative, but not limitative purposes, according to its preferred embodiment, but it is to be understood that variations and/or modifications can be carried out by a skilled in the art, without departing from the scope thereof, as defined according to enclosed claims.