Nanoscale Organic Data Storage using Atomic Force Microscopy

B. Mc Carthy, K. Yamnitskiy, Y. Zhao, G.E. Jabbour, D. Sarid

Optical Sciences Center, University of Arizona, 1630 E. University Blvd., Tucson, AZ 85721. bmccarthy@optics.arizona.edu

Abstract: Recently, the storage industry has begun to explore alternatives to current magnetic hard drive technology, e.g. AFM-based storage. We have been investigating organics storage media, of interest due to their advantageous properties. Results show that these can be written in ~40 ns, suggesting potential as an alternative storage medium. 2003 Optical Society of America OCIS codes: 170.5810 Scanning microscopy, 160.4890 Organic materials

1. Introduction

The demands for data storage have exploded over the past few years with the advent of an increasingly computer-dependent society and the internet. Simultaneously, the capabilities and capacities of commercial data storage, i.e. hard disk drives, have increased exponentially, with data density and transfer rate increasing by nearly an order of magnitude every five years (IBM). The current record for data density is 100 gigabits/square inch, which is rapidly approaching the fundamental physical limit, the superparamagnetic limit. This is the limit at which the bit size reaches the limit of magnetic stability at room temperature. Because of this, and emerging new applications of data storage, new technologies are being explored as successors or complements to hard drive technology [1].

One potential alternative is based on the AFM, well known for its ability to image and manipulate nanoscale structures. The idea of using this technique to read and write data was prototyped as far back as 1991 [2], but has re-emerged in recent years due to several prominent efforts by IBM [3] and Carnegie Mellon [4]. In this paper we investigate the possibility of using AFM to electrically write and read data on organic media that offers several advantages over alternative methods, such as energy efficiency and bit size.

2. Experimental Details

Conducting organic films were prepared by a variety of methods, including spin-coating and physical vapor deposition onto HOPG substrates. The topography and electric conductivity of these films were examined by a conducting-tip AFM. It was found that the application of a short pulse between the tip and organic film induced a local change in conductivity by four orders of magnitude, as shown in Fig. 1.

-2.00x10-7 -1.00x10-7 0.00 1.00x10-7 2.00x10-7 3.00x10-70.000

2.000

4.000

6.000

8.000

10.000

12.000

14.000

Voltage

Time

Fig. 1. Local conductivity change in the organic film as a function of time: The black line indicates the voltage pulse applied to the film while the red line is indicative of the film conductivity before and after the application of the pulse.

These and similar results that will be reported later suggest the potential of electrical switching of thin organic films for data storage. The advantages of the technique are speed, high data density, high S/N, and cost effectiveness.

7. References [1] D. Sarid, B. Mc Carthy, G.E. Jabbour, “Nanotechnology for Data Storage Applications”, (Springer Handbook of Nanotechnology, 1995). [2] H. J. Mamin and D. Rugar, "Thermomechanical writing with atomic force microscope tip," Appl. Phys. Lett. 61 (8), 24 August 1993 [3] P. Vettiger, M. Despont, U. Drechsler, U. Dürig, W. Häberle, M. I. Lutwyche, H. E. Rothuizen, R. Stutz, R. Widmer, and G.K. Binnig,” The "Millipede"—More than thousand tips for future AFM storage”, IBM J. Res. Develop., 44 (3) May 2000 [4] J.L. Griffin, S.W. Schlosser, G.R. Ganger, D.F. Nagle, “Modeling and Performance of MEMS-based Storage Devices”, Proceedings of ACM Sigmetrics, (2000).

ThPP6ThQQ6