OXIDE METAL SEMICONDUCTOR SUPERLATTICES FOR THERMOELECTRICS
Lanthanum strontium manganate (La 0.67 Sr 0.33 Mn0 3 , i.e., LSMO)/lanthanum manganate (LaMn0 3 , i.e., LMO) perovskite oxide metal/semiconductor superlattices were investigated for potential p-type thermoelectric applications. Growth optimizations were performed using pulsed laser deposition to achieve epitaxial superlattices of LSMO (metal)/LMO (p-type semiconductor) on strontium titanate (STO) substrates. In-plane Seebeck results validated the p-type semiconducting and metallic behavior in LMO and LSMO thin films, respectively. Thermal conductivity measurements via the photo-acoustic (PA) technique showed that LSMO/LMO superlattices exhibit a room temperature cross-plane thermal conductivity (0.89 W/m·K) that is significantly lower than the thermal conductivity of individual thin films of either LSMO (1.60 W/m·K) or LMO (1.29 W/m·K).
1 . A method of making an oxide metal semiconductor epitaxial superlattice for use in a thermoelectric application, comprising the step of:
depositing a p-type perovskite oxide on a substrate using a pulsed laser.
2 . The method of claim 1 , wherein the perovskite oxide is selected from the group consisting of general formula 1, general formula 2, and any combination thereof,
general formula 1 having the structure:
ABO 3
general formula 2 having the structure:
A(B X B Y )O 3
where A is a cation selected from the group consisting of rare earth elements and alkaline earth metals,
where B is a cation selected from the group consisting of rare earth elements and transition metals, and
where B X is a cation selected from the group consisting of rare earth elements, and transition metals,
where B Y is a cation selected from the group consisting of rare earth elements, alkaline earth metals, and transition metals,
where the sum of x and y equals 1, and
where O is oxygen.
3 . The semiconductor of claim 2 , wherein A is an alkaline earth metal.
4 . The semiconductor of claim 3 , wherein A is magnesium.
5 . The semiconductor of claim 2 , wherein B is a rare earth element.
6 . The semiconductor of claim 5 , wherein B is lanthanum.
7 . The semiconductor of claim 2 , wherein B X is a rare earth element.
8 . The semiconductor of claim 7 , wherein B X is lanthanum.
9 . The semiconductor of claim 2 , wherein B Y is an alkaline earth metal.
10 . The semiconductor of claim 9 , wherein B Y is strontium.
11 . The semiconductor of claim 2 , wherein the perovskite oxide is in a face centered cubic position.
12 . The semiconductor of claim 2 , wherein the peroskite oxide is utilized as a p-type thermoelectric element.
13 . The method of claim 2 , wherein the substrate is strontium titanate.
14 . The method of claim 2 , wherein the perovskite oxide is selected from the group consisting of lanthanum strontium manganate, lanthanum manganate, and a combination thereof.
15 . The method of claim 14 , further comprising the step of achieving a semi-transparent thin film of lanthanum manganate, wherein the lanthanum manganate is under pressure within the range of approximately 45 mtorr to approximately 55 mtorr.
16 . The method of claim 14 , wherein the combination of lanthanum strontium manganate and lanthanum manganate creates a superlattice, wherein the superlattice exhibits a room temperature cross-plane thermal conductivity of approximately 0.89 W/m-K.
17 . The method of claim 16 , wherein the superlattice exhibits a ZT value over approximately 2.
18 . The method of claim 16 , wherein the superlattice exhibits stability and reliability at high temperatures within the range of approximately 800 K to approximately 1000K.