Structure, chemistry and strength of interfaces

High-resolution electron micrograph of the interface between a YBCO superconducting thin film and the single crystal lanthanum aluminate substrate it was deposited on. The simulated images of the two structures are inset.

Atomic arrangement at the interface between a GaN grain and the (111) Si single crystal it was deposited on.

Heteroepitaxial growth on closely lattice-matched substrates is commonly found in thin film technology. The nature of the film/substrate interface often determines the defect structure in these films, which in turn determines key properties. Our research involves the study of such interfaces, with an emphasis on the formation of dislocations, stacking faults and domains, and their effects on the optical, electrical and adhesion properties.

Another area of interest is the 'reactive element effect', in which the adhesion between an alloy and its thermally grown protective oxide scale can be dramatically improved in the presence of very small quantities of 'rare earths' such as yttrium at the interface. Our research involves quantifying the strength of the interface as a function of its structure and chemistry.

Collaborators

V. Gupta, UCLA

Papers

H. Wu, S.N. Basu, K. Vasilee and V. Gupta, "The Effect of Structure and Chemistry on the Strength of FeCrAl(Y)/Sapphire Interfaces: I. Structure and Chemistry of Interfaces", Accepted for publication in Materials Science and Engineering A, 2002.

H. Wu, S.N. Basu, K. Vasilee and V. Gupta, "The Effect of Structure and Chemistry on the Strength of FeCrAl(Y)/Sapphire Interfaces: II. Strength of Interfaces", Accepted for publication in Materials Science and Engineering A, 2002.

D. Doppalapudi, E. Iliopolous, S. N. Basu and T. D. Moustakas, "Epitaxial Growth of Galliuim Nitride Thin Films on A-Plane Sapphire by Molecular Beam Epitaxy", Journal of Applied Physics, 85 (7), 3582 (1999).

D. Doppalapudi, E. Iliopoulos, S. N. Basu and T. D. Moustakas, "Effect of Nitridation and Buffer in GaN Films Grown on A-Plane (11-20) Sapphire", Materials Research Society Symposium Proceedings, 482, 51 (1998).

S. N. Basu, T. Lei and T. D. Moustakas, "Microstructures of GaN Films Deposited on (001) and (111) Si Substrates Using Electron Cyclotron Resonance Assisted Molecular Beam Epitaxy", J. Materials Research 9 (9), 2370 (1994).

S. N. Basu, "A Study of Microstructures of YBa2Cu3O7-x Thin Films", Proceedings of the International Conference on Beam Processing of Advanced Materials, J. Singh and S. M. Copley eds., TMS, pp 333 (1993).

S. N. Basu, A. H. Carim and T. E. Mitchell, "A TEM Study of Microstructures in YBa2Cu3O7-x Thin Films Deposited in LaAlO₃ by Laser Ablation", J. Materials Research 6 (9), 1823 (1991).

Funding

NSF - Study of the Strength of Interfaces at Elevated Temperatures and its Relationship to Interfacial Structure and Chemistry(with V. Gupta).

LANL - Structure of Ferroelectric Superconducting Interfaces.