High-resolution Magnetic Force Microscope

Transcription

1 High-resolution Magnetic Force Microscope hr-mfm Gigasteps on a nanoscale hr-mfm the key instrument for research and development of high-density magnetic media. 1 nm magnetic resolution guaranteed. Winner of

2 Quantum leap in hard disk technology Especially designed for research, development and quality control of magnetic storage media and other magnetic material, the hr-mfm is an analytical and quantitative magnetic imaging system. Its exceptionally high magnetic resolution of 1 nm or better matches the best results obtained by SEMPA (Scanning Electron Microscopy with Polarization Analysis) on disk media. The hr-mfm features fast mounting of hard disk platters and a coarse positioning system with a radial accuracy of 1 nm and an angular accuracy of.2 on the entire disk area. The two available metrology scanners, one for a scan range of 12 µm 12 µm and the other for a scan range of 4 µm 4 µm, are fully linearized. The microscope can be operated at ambient temperature as well as in high vacuum. Its vacuum pumping system includes a turbomolecular pump and a membrane pump ensuring high-vacuum conditions with easy maintenance and a pump-down time of less than 1 minutes. The vibration and acoustic isolation system is electronically controlled. The different operational modes include a true non-contact mode as well as the ability to reverse the tip magnetization for excellent separation of topographic and magnetic information. NanoScan developed a new proprietary software and control system with the main focus on user-friendliness and a wide range of SPM-modes. A fully digital PLL system with high frequency stability was implemented. The sample can be mounted easily and the cantilever alignment is completely motorized.

3 Probing the future of data storage The hr-mfm is a key instrument in the improvement of the current hard disk technology and is optimized for research and development departments of the data storage industry. In Research Centers and Universities it is an excellent tool to analyze surface structures and to characterize new magnetic materials and thin film technology, for example magnetic quantum dots and layered nanostructures for mram and FeRAM applications. Scope of delivery Instrument hr-mfm, vacuum system, vibration and acoustic isolation system, electronics rack, piezo motor controller, workdesk Controller and software hr-mfm controller with proprietary real-time software (ScanEngine), Windows workstation with two 19 monitors, scan software package (ScanDirector), free updates for one year Accessories Video System with one camera for cantilever adjustment, tip holder, dummy sample holder, disk mounting lock, high-resolution magnetic tips, tip magnetization unit Optional items Additional video system for easy tip positioning and sample observation, software package for quantitative magnetic analysis, piezo-response mode for measuring polarization on ferroelectric samples, adjustable in-situ magnets for application of an external field (in-plane or perpendicular) to sample and tip, thermal stage for cooling or heating the sample Services Measurement training, local technical support, training workshops Total view of hr-mfm.

4 Hard disk pattern f [Hz] 1 f [Hz] [nm] nm 1nm [nm] Top left: 2 µm 2 µm image. Top right: 59 nm 59 nm zoom image with two cross-sections. Bottom left: Cross-section 1 with domains magnetized opposite to the direction of the written bit. Bottom right: Cross-section 2 with two ultrasmall domains near the track edge with 1 nm and 15 nm diameter, respectively Magnetic nanodots The individual magnetic FePt nanodots of 7 nm size and 3 nm height in a regular hexagonal pattern show an internal domain pattern. The magnetic image revealing the nanomagnetic structure of the dots was taken in high-resolution MFM mode. 1 nm The line section through the magnetic image (yellow line) 2 4 matches with the same section through the contact-mode topographic image (blue line). Sample by courtesy of J. Yuan; Tsinghua Univer sity, China Magnetic Frequency Shift (Hz) nm FWHM 1 nm Topographic Height (nm)

5 f [Hz] nm [nm] f [Hz] nm 1nm [nm] High-resolution Magnetic Force Microscopy on perpendicular media measured at Seagate Research Laboratory, Pittsburgh. Top left: Top right: Bottom: 2.5 µm 2.5 µm image. 7 nm 7 nm zoom image with two cross-sections. Cross-section 1 and 2 with ultrasmall domains with 1 nm diameter. Interior view with cantilever holder. Performance testing NanoScan provides a special service for interested customers. Samples may be submitted for test measurements in order to prove the performance of the hr-mfm. The customer will receive prompt delivery of two images of the magnetic patterns measured.

6 Carbon nanotube S N N S N S N S 1 µm Structural and magnetic properties of a Fe-filled carbon nanotube: 1st: Shape imaged with secondary electrons in scanning electron microscopy. 2nd: Topography imaged with hr-mfm in intermittent-contact mode gives real dimension and height information. 3rd: Different material contrast of carbon nanotube and environment is visible in hr-mfm electrostatic force mode. 4th: Magnetic image shows the monopoles of different magnetic dipoles inside the nanotube. Data acquired with hr-mfm in high-resolution MFM mode with original and inverted tip magnetization and subsequent calculation of the pure magnetic contribution. SEM-images by courtesy of A. Winkler, S. Menzel, R. Kozhuharova-Koseva, S. Hampel, A. Leonhardt, B. Büchner, T. Mühl, Leibniz Institute of Solid State and Materials Research IFW Dresden, Germany 5th: Bright sections indicate the locations of Fe-filling inside the nanotube. They are matching with the magnetic image. Data acquired with backscattered electrons of scanning electron microscopy.

7 Patterned magnetic multilayers Narrow magnetic lines produced by e-beam lithography and imaged with high-resolution MFM mode: Most lines are a single magnetic domain, but some contain a domain wall with the respective flip of magnetization. Image size is 4 µm 1 µm. Square dots of a patterned magnetic multilayer system measured with high-resolution MFM mode: Most dots are magnetic monodomains, but some show an internal domain structure. Both polarities (bright and dark) of mono-domain dots are present. Image size is 8 µm 8 µm. Samples by courtesy of B. Belle; EISS group at University of Manchester, UK Piezo-response mode on ferroelectric PZT Ferroelectric domains can be imaged using the piezo-response mode. For that purpose, the scan is done in contact mode with an additional oscillatory bias potential at the tip. The piezoelectric response is then demodulated from the cantilever oscillation. The three images (1 µm 1 µm size) of a polycrystalline PZT sample show complementary information and were simultaneously measured. Sample and measurement by courtesy of R. Thapliyal, H. J. Hug; Empa Materials Science and Technology, Switzerland Topography of the PZT grains Domain pattern of normal polarization Domain pattern of lateral polarization

8 Exchange bias system Patterned exchange-bias system with elliptic dots of a 8 nm IrMn antiferromagnetic layer on top of a 3 nm CoFeB ferromagnetic layer with 1 nm Ta capping. 1 µm 1 µm Sample by courtesy of N. Wiese, M. Rührig, J. Wecker; Siemens AG Corporate Technology, Germany The topography shows regular dots with grainy defects at the borders. Measurement taken by contact-mode AFM in vacuum. In the magnetic image, the in-plane dipole moment from the ferromagnetic films produce the black and white edges on the left and right of the dots. The additional magnetic contrast visible within the dots is generated by the coupling to the anti-ferromagnetic layer. Comparison of dots with and without the antiferromagnetic IrMn layer. 2 nm 2 nm Hz µm Hz µm The ferromagnetic CoFeB layer alone shows the expected dipolar contrast at the edges of the dot with a flat contrast inside the dot. The exchange-biased system shows additional magnetic features inside the dot that can be attributed to uncompensated spins in the anti-ferromagnetic IrMn layer. Sample by courtesy of N. Wiese, M. Rührig, J. Wecker; Siemens AG Corporate Technology, Germany

9 Software overview Main control window of ScanDirector with a frequency sweep of the cantilever resonance and an image scan of a hard disk pattern. The ScanDirector provides a user-friendly Windows based operating environment to control the ScanEngine, which is a crash-safe real-time system that controls feedback loops and scans. Direct access and maximum visibility of all signals and parameters allow full control, and yet the user interface is kept simple and clear. Color coding of fields helps to direct the user s attention to important parameters. The main window contains the three feedback controls «z-control», «Amplitude Control», and «Phase-locked Loop», which can be configured for any common static or dynamic AFM mode plus true non-contact mode and highresolution MFM mode. A «Frequency Sweep» window demonstrates the high quality factor of the cantilever in vacuum. The resonance peak at Hz has a width of 1.5 Hz, resulting in a Q-factor of 27. In the «Small Top Views» window a forward and backward scan of a 1 µm 1 µm area of a harddisk test pattern is shown. The measurement was carried out in high-resolution MFM mode.

10 High-resolution magnetic tips The magnetic sensors are key elements of the hr-mfm. Our high-aspect ratio tips are magnetically coated using a proprietary manufacturing process.

11 Performance and specifications System active vibration isolation table additional internal vibration isolation of microscope easy to handle pumping system (pump-down < 1 min) operation in ambient conditions and in < 1-5 hpa vacuum thermal and acoustic insulation, thermally compensated Swiss precision mechanics in-situ illumination and large viewports for excellent visibility Scanning fully linearized metrology scanner with range options of - 12 µm x 12 µm x 2 µm - 4 µm x 4 µm x 6 µm linearity better than.5% lateral resolution.2 nm normal resolution.3 nm magnetic resolution 1 nm Tip stage 4-quadrant beam deflection system for normal and lateral force measurements fully motorized cantilever and beam alignment stage accommodates all standard cantilevers rapid exchange of cantilevers with repositioning precision better than 1 µm Sample stage optimized for disks of up to 12 mm diameter with quick mounting lock several smaller sized samples are fixed on dummy disk radial positioning range of 4-65 mm on full 36 circle repeatability and relative precision of 1 nm radially and.2 angular Controller and software ScanDirector: user-friendly Windows-based software ScanEngine: crash-safe real-time system for instrument control and scanning fully digital phase-locked loop (PLL) for highest sensitivity measurements and cantilever resonance frequencies up to 3 MHz all common static and dynamic AFM modes plus true non-contact mode and high-resolution MFM mode data acquisition of up to 16 simultaneous signal channels unrestricted number of measurement points and lines with online zooming and panning of large images TipGuard: safety conditions prevent tip sample contact and tip damage Opened vacuum chamber. Folded back microscope for exchanging cantilevers. Specifications subject to change without notice

12 Applied nanotechnology for the global industry NanoScan Ltd, a spin-off company of the University of Basel (Switzerland), commercializes nanotechnology by developing new products, solutions and application segments as well as by optimizing current methods. Its purpose is to provide the global market with high-resolution scanning probe microscopes fulfilling present and future analytical needs on nanometer-sized surface structures. Merging top-level scientific research with state-of-the-art technology and management competence, NanoScan ist a highly specialized company in the realm of investment goods. Its products stand out due to their performance, quality and user-friendliness. The company benefits from its in-depth knowledge in nanotechnology and the synergies between its partners in science and industry. As the winner of the Swiss Technology Award 23 for manufacturing an innovative prototype of a high-resolution magnetic force microscope, NanoScan has proved its ability to venture into new dimensions of nanotechnology. 2 nm A. Moser et al. (Hitachi GST) Journal of Magnetism and Magnetic Materials 33 (26) 271 NanoScan Ltd Überlandstrasse Dübendorf Switzerland Phone Fax info@nanoscan.ch