Buffer layer for the crystal growth of metal oxides of perovskite type in particular on amorphous substrates
A multilayer conductive system of metal oxides, the system including a substrate; a layer of a crystalline binary metal oxide deposited on the substrate, and a layer of a crystalline conductive metal oxide having a crystalline structure of perovskite type superposed over the layer of binary metal oxide, where the binary metal oxide of the layer has a local lattice mismatch of less than 5% with respect to that of the metal oxide of the layer, provided that when the metal oxide of perovskite type of the layer is a crystalline transparent conductive metal oxide, the substrate is transparent, and the thickness of the crystalline binary metal oxide layer is <20 nm, preferably <10 nm, most preferentially 5-7 nm.
1 . A multilayer conductive system of metal oxides comprising:
i. an amorphous substrate;
ii. a layer of a crystalline binary metal oxide deposited on the substrate (i); and
iii. a layer of a crystalline conductive metal oxide having a crystalline structure of perovskite type superposed over the layer of binary metal oxide (ii);
the binary metal oxide of the layer (ii) having a local lattice mismatch of less than 5% with respect to that of the metal oxide of the layer (iii);
provided that when the metal oxide of perovskite type of the layer (iii) is a crystalline transparent conductive metal oxide, the substrate (i) is transparent and the thickness of the crystalline binary metal oxide layer (ii) is <20 nm.
2 . The multilayer conductive system according to claim 1 , wherein the metal oxide of perovskite type of the layer (iii) comprises:
A. a crystalline transparent conductive metal oxide having a formula ABO 3 wherein A is selected from Sr or Ca optionally doped with La or another element from the group of lanthanides, and B is selected from V, Cr, Ti or Mo;
B. a manganite with colossal magnetoresistance of perovskite structure with the formula Ln (1-x) A x MnO 3 wherein Ln represents a rare earth atom, A is selected from alkaline earth atoms and x represents a doping level of the alkaline earths, or C. a ferroelectric metal oxide of perovskite structure with the formula ABO 3 , wherein A is selected from Ba, Pb or K, and B is selected from Ti, Zr or Ta.
3 . The multilayer conductive system according to claim 1 , wherein the metal oxide of perovskite type of the layer (iii) comprises a ferroelectric oxide (C), and:
(i) the binary metal oxide of the layer (ii) is a conductive binary metal oxide; or
(ii) the binary metal oxide of the layer (ii) is an insulating binary metal oxide, the substrate (i) is a conductive substrate;
the multilayer system further comprising a conductive layer (cc) superposed over the layer (iii).
4 . The multilayer conductive system according to claim 3 , wherein the conductive layer (cc) comprises a conductive material selected from at least one of:
a conductive metal oxide comprising TiO 2 or O-substoichiometric ZnO;
a conductive perovskite oxide; or
a conductive metal layer, comprising a layer of gold, silver, or aluminum.
5 . The multilayer conductive system according to claim 1 , wherein the substrate (i) is transparent, the crystalline binary metal oxide layer (ii) has a thickness <20 nm, and the crystalline conductive metal oxide of perovskite type of the layer (iii) is transparent, and wherein
the system further comprises a transparent layer (ct) superposed over the layer (iii) of conductive metal oxide, said transparent layer (ct) being a layer of a conductive metal oxide or an insulating oxide, the layer (ct) covering all or part of the layer (iii).
6 . The multilayer conductive system according to claim 1 , wherein the crystalline binary metal oxide of the layer (ii) is selected from at least one of the following oxides: SnO 2 , ZnO, Y 2 O 3 , ZrO 2 , HfO 2 , Cr 2 O 3 , and TiO 2 .
7 . The multilayer conductive system according to claim 5 , wherein the layer (iii) of transparent conductive metal oxide has a thickness of 20 to 100 nm.
8 . The multilayer conductive system according to claim 5 , wherein the transparent crystalline conductive metal oxide of perovskite type of the layer (iii) has a formula ABO 3 and is doped on the A-site with Ca, La, or other lanthanides;
and/or on the B-site with Ti, Cr, Mo, or other transition metals.
9 . The multilayer conductive system according to claim 5 , wherein the transparent crystalline conductive metal oxide of perovskite type of the layer (iii) has a formula ABO 3 and is selected from SrVO 3 , SrCrO 3 and SrMoO 3 optionally doped with Ca, La, or other lanthanides on the “Sr” site; or CaVO 3 optionally doped on the “Ca” site with Sr, La, or other lanthanides.
10 . The multilayer conductive system according to claim 5 , wherein the transparent substrate (i) is an amorphous transparent material having a temperature resistance of 500° C.
11 . The multilayer conductive system according to claim 5 , which has an optical transparency in the visible region >70%.
12 . An electronic component comprising a multilayer conductive system of metal oxides according to claim 1 .
13 . A method for preparing the multilayer conductive system of metal oxides according to claim 1 , comprising:
(a) depositing on an amorphous substrate, optionally transparent, a layer of a crystalline binary metal oxide;
(b) the crystal growth of a layer of a crystalline conductive metal oxide on the crystalline binary oxide layer obtained in step a), wherein the conductive metal oxide has a crystalline structure of perovskite type; and
(c) optionally coating the conductive metal oxide layer obtained in b) with a protective layer (cp), optionally transparent, of a conductive metal oxide or an insulating oxide,
the layer obtained in c) covering all or part of the conductive metal oxide layer obtained in b);
the binary metal oxide of step a) having a local lattice mismatch of less than 5% with respect to that of the crystalline conductive metal oxide of perovskite type of step b);
provided that when the metal oxide of perovskite type of the layer of step b) is a crystalline transparent conductive metal oxide, the substrate of step a) is transparent and the thickness of the crystalline binary metal oxide layer of step a) is <20 nm.
14 . The method according to claim 13 , wherein step a) is carried out by a thin layer deposition technique comprising at least one of vacuum cathode sputtering, molecular beam epitaxy or chemical vapor deposition techniques comprising metalorganic chemical vapor deposition or atomic layer deposition.
15 . The method according to claim 13 , wherein step b) is carried out at a temperature ≥400° C., by pulsed laser deposition, by vacuum cathode sputtering, by molecular beam epitaxy or by chemical vapor deposition techniques comprising at least one of metalorganic chemical vapor deposition or atomic layer deposition, or by pulsed laser ablation.
16 . The multilayer conductive system of metal oxides according to claim 1 , configured for use:
in optoelectronics;
in solar technologies comprising solar cells or panels;
in sensor technology, comprising touch sensors;
in display technologies comprising liquid crystal screens, flat screens, plasma screens, and touch screens;
in infrared reflective coatings comprising infrared filters/mirrors or glazing/glazing units with low emissivity;
in electromagnetic shielding,
in transparent electronics;
in integrated antennas; and/or
in conductive substrates for integrated circuits.
17 . The multilayer conductive system according to claim 1 , wherein the metal oxide of perovskite type of the layer (iii) comprises a ferroelectric oxide (C), and the binary metal oxide of the layer (ii) is an insulating binary metal oxide, the substrate (i) is an optionally transparent insulating substrate, and the system further comprises an additional conductive layer (iv) located between the substrate (i) and the layer (ii) of binary metal oxide;
the multilayer system further comprising a conductive layer (cc) superposed over the layer 111 ).
18 . The multilayer conductive system according to claim 17 , wherein the conductive layer (cc) comprises a conductive material selected from at least one of:
a conductive metal oxide comprising TiO 2 or O-substoichiometric ZnO;
a conductive perovskite oxide; or
a conductive metal layer, comprising a layer of gold, silver, or aluminum.