1. Hydrothermal Processing of Ba X Sr (1-X) TiO 3 Presented By: Adam Chamberlain Advisors: Elliot Slamovich Mark McCormick

2. Outline Applications Background Procedure Results –Composition vs. Leakage, Dielectric Constant & Loss –Annealing vs. Leakage, Dielectric Constant & Loss –Thickness Reduction –Dopant effect Conclusions Acknowledgements

3. Applications BST’s tunable  ´, high dielectric strength, low leakage and loss has made it desirable in electrical applications –Dynamic random access memory (DRAM), multilayer capacitors, microelectromechanical systems (MEMS)

4. Background BST is processed using sputtering, MOCVD, or CSD –These methods sometimes require high vacuum systems or heat treatments above 500 o C Hydrothermal processing allows for crystalline BST to form at temperatures below 100 o C

5. Procedure Titanium Dimethoxy Dineodeconate (TDD) is used as the precursor TDD is spin-coated onto a Pt coated glass substrate After each layer the precursor is pyrolyzed at 400 o C SiO 2 Pt TiO 2 ~300 nm

6. Films are reacted in Ba,Sr(OH) 2 (aq) @ 90°C for 24 h Using (110) XRD peak the composition is determined (Vegard’s Law) Photolithography is used for sputtering Pt electrodes onto surface Electrical contact are made to form planar capacitors SiO 2 Pt BST Pt

7. 1  m BST Pt SiO 2 1  m Planar SEM micrograph Cross-section SEM micrograph

8. Optical micrograph of electroded sample

9. Using a LCR meter tan  and capacitance are measured at room temperature DC voltage is applied and the resulting leakage current is measured (I-V curve)

10. Results Composition vs. leakage, dielectric constant & loss Annealing vs. leakage, dielectric constant & loss Thickness Reduction Dopant effect

11. Composition vs. Leakage %Ba(OH) 2 in solution

12. Composition vs. Dielectric Constant

13. Composition vs. Dielectric Loss

14. Annealing vs. Leakage Data from sample 50-4

15. Data from sample 90-4

16. Types of conduction –Ohmic –Schottky –Poole-Frenkel If Poole-Frenkel contributes to leakage then removal of defects should reduce it

17. Annealing vs. Dielectric Constant

18. OH - are on oxygen sites –Ion jump polarization is available Annealing removes OH - –Ion jump not available –Decrease in  O O 2-__ H + O O O O AC

19. Annealing vs. Dielectric Loss

20. Thickness Reduction Reducing thickness increases capacitance Thickness is limited by particle size pH Reaction Temperature Precursor thickness

21. Planar view of barium titanate thin film Cross-section of barium titanate thin film (~85 nm)

22. Dopant Effect Five atomic percent of magnesium oxide was added to the precursor Magnesium will sit on barium or titanium sites Ba Ba Mg Ba Ti Ti + O O Mg Ti + V O xx x x-2..

25. Conclusions Composition does not effect the electrical properties Annealing decreases the dielectric constant, loss, and leakage Small additions of Mg increases the dielectric constant

26. Acknowledgements Dr. Elliot Slamovich Mark McCormick Purdue University