Super-High Density Optical and Magnetic Memory
Study for Possible Design of Optical and Magnetic Memory with Super-High Recording Density with the Use of Femtosecond Laser Radiation and Atomic-Force Microscopy
Tech Area / Field
- INF-DAT/Data Storage and Peripherals/Information and Communications
8 Project completed
Senior Project Manager
Russian Academy of Sciences / Institute of Applied Physics, Russia, N. Novgorod reg., N. Novgorod
- VNIIEF, Russia, N. Novgorod reg., Sarov\nInstitute of Physics of Microstructures, Russia, N. Novgorod reg., N. Novgorod
- Los Alamos National Laboratory, USA, NM, Los-Alamos\nNano optical data storage center (NANO-DISC), Korea, Yusong Gu
Project summaryDevices of optical and magnetic memory are considered to be an important element of any state-of-the- art communications equipment. The increasing of information recording density is obviously one of the main avenue to improve thereof. Nowadays, commercial storage devices have the recording density of 26 Gbyte/ inch2, and in the nearest future this density is suggested to be reached 100 Gbyte/inch2 . A number of companies are engaged in work of perspective designs, so that the recording density can be increased as high as 1Tbyte/inch2. For example, IBM company performs scientific work on the formation of nanostructures of about 10 nm . By this technique, data is recorded on the surface of a thin elastic foil by means of a microneedle matrix (“multileg” technology). The microneedle tips are heated to temperature of 400°, and then melt the polymer film making points on it. The first demonstrated prototype of the “multileg” technique with 1024 needles has the memory of 0.5 Gbyte with a recording area of 3×3 mm2 (recording density 30 Gbyte/inch2).
Recent years, to increase the recording density, investigations in designing nanostructures on the surface of solid specimen through the use of laser and atomic-force microscopy techniques are in progress [3, 4]. So, in works [3 - 9] it was shown, that pits or hillocks of a specific diameter d ~ (20 – 50) nm (what is much less than the laser wavelength) and vertical size of several nanometers were found on the surface of the foils from gold, copper and polymethylmethacrylate. Despite the fact that the formation of nanostructures on the specimen surface when irradiating the scanning microscope probe was investigated by many researchers (see, for instance, the review ), there is no unique understanding what mechanism is responsible for this process.
To tackle the problem of gaining in data record density, two techniques being at the front of the scientific development: femtosecond laser and atomic-force microscopy are proposed to be used in this project. The application of femtosecond light pulses will enable to explore the effect of pulse duration on the nanostructure formation, what is important in elucidating the mechanism of their generation. Preliminary experiments have shown that with femtosecond radiation, one manages to obtain nanostructures in such solid and high-melting materials, as FeCr.
The idea of this method is as follows. The tip of the atomic-force microscope (the tip curvature radius r ~ 10-30 nm) is positioned close to the surface where nanostructures are likely to be formed. The gap between the tip and surface is illuminated by a femtosecond laser. In the laser light, on the surface of specimen below the probe tip, nanostructures are set off. Experiments conducted following the scheme described above both in our laboratory with the use of femtosecond laser radiation, and in other laboratories using long-pulse lasers, showed that as a result of the exposure of the specimen to laser radiation, nanostructures (pits or hillocks) with nanometric sizes (structure diameter d = 30-80 nm) on the surface are formed.
Preliminary experiments performed in our laboratory have shown that the application of laser pulses of femtosecond duration makes it possible to extend the range of materials where nanostructures can be generated. In particular, there were created structures with a diameter d = 50-60 nm on the surface of the foil fabricated from a solid and high-melting magnetic material - FeCr . In the proposed project, detailed investigations in finding optimal conditions to generate nanostructures, best pairs of the probe material and processed specimen foils are expected to carry out. The feasibility study of further decrease in sizes of generated nanostructures is likely to perform. Of great importance is the elucidation of the mechanism of the nanostructure formation on the surface. The implementation of the proposed range of experimental tasks will enable to make steps on the road of developing storage elements with the record density exceeding terabyte per square centimeter (і 1 Tbyte/cm2). Successful realization of the project will open the opportunity for the development of radical fundamentals of process equipment to design storage elements of a new generation.
To investigate the feasibility of creating optical and magnetic memory devices of super-high (~ Tbyte/cm2 recording density based on nanostructures with the use of femtosecond laser radiation, and atomic-force microspectroscopy, a number of tasks are required to tackle. Key tasks are as follows:
Task 1. Experimental investigations aimed at elucidating of mechanisms of the generation nanostructures generation on exposure of the active zone of the atomic-force microscope to laser pulses of femtosecond duration.
Task 2. Optimization of regimes of laser radiation of femtosecond duration with the goal of minimizing the sizes of nanostructures.
Task 3. Making choice among various materials for the tip of the atomic-force microscope and samples with the purpose of minimizing the sizes of nanostructures and increasing the technological effectiveness.
Task 4. Study on the formation of nanostructures on the surface of magnetic materials.
Task 5. Demonstration of feasibility to design nanostructures with sizes giving effective density of recording up to ~ 1 Tbyte/cm2.
The Project objective is to implement these tasks.
The leading institution responsible for the project activities is IPF RAN. Its workers have high skills in theory and experiment in the field of the development and application of femtosecond laser systems, and also in atomic-force microscopy research. At IPF RAN, efforts are underway to employ femtosecond lasers, including the experiments for generation of nanostructures on the surface of various materials [11-16].
The participating institution, RFNC-VNIIEF, will perform design and technological development, and also manufacture models of experimental facilities and designed prototypes, participate in experimental investigations and assessment of results. This institution’s staff who takes part in the project activities has experience in design and manufacture of various optoelectronic and optical and mechanical units of the laser facilities [17-23].
Other participating institution, IFM RAN, has a high experience in (1) a thin-layer technology, (2) scanning probe microscopy (including magneto-force microscopy) and (3) electronic microscopy [24-31]. The institution workers participating in the project activities, will (1) carry out investigations for feasibility of formation magnetic nanostructures employing the proposed approach, (2) test shape of the tips apex and their modification upon interacting with the specimens being developed.
The main content of the Project relates to applied studies.
The project will enable to achieve a number of ISTC main objectives:
- A large team of former weapons scientists and engineers will have an opportunity to redirect to peaceful activities. 21 weapons scientists will take part in the project.
- There will be obtained a significant amount of new scientific information accessible to those who will take an interest in it.
- The project will promote the integration of Russian scientists into the international scientific community. The Project activities will be based on the experience, methodology, and capabilities having been gained by the participating institutions.
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