Applying NiTi Shape-Memory Thin Films to Thermomechanical Data Storage Technology
- PDF / 142,315 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 62 Downloads / 135 Views
W1.7.1
Applying NiTi Shape-Memory Thin Films to Thermomechanical Data Storage Technology Wendy C. Crone1, Gordon A. Shaw2 Department of Engineering Physics, University of Wisconsin-Madison, Madison, WI, USA 2 Manufacturing Metrology, National Institute of Standards and Technology, Gaithersburg, MD, USA
1
ABSTRACT As the data storage density in cutting edge microelectronic devices continues to increase, the superparamagnetic effect poses a problem for magnetic data storage media. One strategy for overcoming this obstacle is the use of thermomechanical data storage technology. In this approach, data is written by a nanoscale mechanical probe as an indentation on a surface, read by a transducer built into the probe, and then erased by the application of heat. An example of such a device is the IBM millipede, which uses a polymer thin film as the data storage medium. It is also possible, however, to use other kinds of media for thermomechanical data storage, and in the following work, we explore the possibility of using thin film Ni-Ti shape memory alloy (SMA). Previous work has shown that nanometer-scale indentations made in martensite phase Ni-Ti SMA thin films recover substantially upon heating. Issues such as repeated thermomechanical cycling of indentations, indent proximity, and film thickness impact the practicability of this technique. While there are still problems to be solved, the experimental evidence and theoretical predictions show SMA thin films are an appropriate medium for thermomechanical data storage. INTRODUCTION Because of its physical and chemical robustness, NiTi shape memory alloy (SMA) is the most widely used of the shape memory materials. NiTi derives its unusual mechanical properties, including its ability to recover large amounts of strain by the shape memory effect, through a solid state phase change known as a martensitic transformation. Although it has been widely studied [1], opportunities still remain for the discovery of new behavior and new applications. The micrometer to macroscopic-scale behavior of NiTi has been explored using uniaxial tensile and compressive loading as well as microindentation for both single crystal and polycrystalline samples [2,3]. The micrometer to nanometer-scale behavior of NiTi can also be addressed through indentation techniques. Indentation shape recovery through the shape memory effect in NiTi has been demonstrated on the microscale [4] and the nanoscale [5,6]. Our work also demonstrates a significant increase in the material’s ability to recover at depths less than 100 nm [5]. This capacity of NiTi to deform under indentation and subsequently recovery the majority of the indentation depth with heating opens the possibility that it can be used as a thermomechanical data storage medium. The superparamagnetic limit poses a problem for current high-density magnetic digital information storage media. IBM has invented one possible workaround. The Millipede uses an array of microfabricated cantilevers similar to those used in atomic force microscopy (AFM) to
Data Loading...
