AVS 45th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuM

Paper TF-TuM3
Molecular Dynamics Analysis of Energy Modulated Deposition of Model GMR Materials

Tuesday, November 3, 1998, 9:00 am, Room 310

Session: Thin Films for Sensing and Data Storage
Presenter: H.N.G. Wadley, University of Virginia
Authors: H.N.G. Wadley, University of Virginia
X.W. Zhou, University of Virginia
Correspondent: Click to Email
Vapor deposited multilayers consisting of low electrical resistivity conductors sandwiched between ferromagnetic metals exhibit giant magnetoresistance (GMR). The best GMR properties are obtained from materials with flat interfaces and low intermixing between adjacent layers. Interfacial roughness and intermixing are sensitive to the deposition method and process conditions. A three dimensional molecular dynamics model has been developed and used to establish the relationship between the multilayer nanostructure and vapor deposition conditions, including incident atom angle, incident atom energy and substrate rotation. The results indicate that at low incident energies (e.g., 1 eV or below), an increase in the incident angle leads to a significant increase in the interfacial roughness (and even to void formation) due to a shadowing effect. The development of interfacial roughness was also found to be accompanied by an increase in intermixing. The high interfacial roughness formed during oblique, low energy deposition can be significantly reduced by substrate rotation. High incident atom energies were found to result in a lower interfacial roughness, but at the expense of increased intermixing caused by an atomic exchange mechanism. Under normal incidence conditions, an intermediate incident energy of between 1 and 2 eV resulted both in a low interfacial roughness and intermixing. The simulation methodology was used to explore the benefits of modulated incident energy deposition strategies. When thermal energy adatoms were used to deposit the first few monolayers of each new metal layer, intermixing by the exchange mechanism during subsequent hyperthermal energy deposition could be eliminated, and films with almost no interfacial roughness or intermixing could be grown over a wide incident angle range.