Xidex application note cnt afm tip fabrication using the nano bot system - 110313

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A carbon nanotube (CNT) attached to the end of a conventional silicon (Si) atomic force microscope (AFM) tip enables scanning with higher spatial resolution and less tip wear than would otherwise be …

A carbon nanotube (CNT) attached to the end of a conventional silicon (Si) atomic force microscope (AFM) tip enables scanning with higher spatial resolution and less tip wear than would otherwise be possible. The exceptional ease of use and mechanical stability of the NanoBot system make it possible to quickly accomplish this important nanofabrication task inside a scanning electron microscope (SEM).

Xidex manufactures and sells the NanoBot® system, an easy-to-use, highly versatile, user programmable nanomanipulator featuring specialized end-effectors for nanodevice fabrication and testing inside scanning electron microscopes (SEMs) and focused ion beam (FIB) tools.

Our mission is to enhance the R&D productivity of nanoscientists and nanotechnologists in both industry and academia. We offer best-in-class turnkey solutions to customers with well-defined requirements that are stable over time, and highly adaptable solutions to customers who need a system that can easily be augmented with additional plug-and-play nanopositioners and end-effectors as their needs evolve.

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  • 1. Xidex Carbon Nanotube AFM Tip Fabrication Using the NanoBot® System Application Note Vladimir Mancevski Xidex Corporation Introduction A carbon nanotube (CNT) attached to the end of a conventional silicon (Si) atomic force microscope (AFM) tip, as shown in Figure 1, enables scanning with higher spatial resolution and less tip wear than would otherwise be possible. The NanoBot system’s exceptional ease of use and mechanical stability make it possible to quickly accomplish this important nanofabrication task inside a 500 nm scanning electron microscope (SEM). 500 nmFigure 1. CNT attached to a Si AFM tip. Figure 2 shows a NanoBot Model NX- 2000, which has two XYZ positioners, mounted on the door assembly of an SEM. This mounting option leaves the SEM sample stage free for use in the nanofabrication process. Only one of the Figure 4. Mounting of a sharp W tip on the XYZ positioners is required to fabricate a NanoBot end effector. CNT AFM tip using the method described in this Application Note. a different level of speed and corresponding responsiveness. The Sample Preparation NanoBot’s Multi Step mode is used to A CNT source and an AFM tip are rapidly maneuver the W tip in XYZ toward mounted on a standard SEM sample the CNT source as shown in Figure 5.Figure 2. A NanoBot Model NX-2000 mounted holder using SEM tape as shown in Multi Step mode enables up to 15 mm ofon the door assembly of an SEM. Figure 3. The CNT source is a silicon XYZ travel. Both Multi Step mode and chip on which CNTs have been grown Single Step mode are used to maneuver using chemical vapor deposition (CVD). the W tip until it is within a few µm of the Multiple AFM tips can also be mounted source of CNTs. Single Step travel is this way for batch fabrication. A sharp CNT AFM tungsten (W) tip is mounted on the Source Tip NanoBot end effector, as shown in Figure 4. The SEM door is then closed and the W Tip sample chamber is pumped down. Picking Up a CNT with the W Tip Nanomanipulator motion control in all CNT three axes is accomplished with a simple Source joystick interface. There are three modes of linear motion, each withFigure 3. AFM tip and CNT source Figure 5. W tip approaching CNT source. 1
  • 2. adjustable from 100 nm to 2 µm. The CNT source is thenexamined by moving the SEM stage until a straight CNT isfound which is extending outward so that it can be easily W Tipaccessed as shown in Figure 6. This procedure typicallyrequires only a few minutes. The NanoBot system’s Fine CNTMotion mode is then used to touch the W probe to theselected CNT, as shown in Figure 7. The required highdegree of mechanical stability is enabled by the NanoBotsystem’s extremely low drift, on the order of 10 nm perminute, in all three axes. The Fine Motion mode enables ±3.5 µm of motion with 1 nm resolution in XYZ. It normallytakes about 30 seconds to bring the W tip into welloriented contact with a selected CNT. Next, the CNT iswelded to the W tip using electron beam induced Figure 8. CNT separated from substrate using current pulse.deposition (EBID) of carbon. Attaching the CNT to the AFM Tip The W tip carrying the CNT is rapidly translated in XYZ to CNT within a few microns of the AFM tip apex, as shown in Source Figure 9. The NanoBot system’s Fine Motion mode, is then used to place the CNT along the side of the silicon W Tip AFM tip apex, as shown in Figure 10. CNT AFM Tip W TipFigure 6. W tip maneuvered to within a few µm of a CNT. CNT Source Figure 9. W tip carrying CNT translated to within a few µm of the AFM tip. CNT W Tip AFM TipFigure 7. W tip in contact with the selected CNT. CNT W TipSeparating the CNT from the CNT SourceAn electrical current pulse is used to separate the CNTfrom the CNT source substrate on which it was originallygrown, as shown in Figure 8. Figure 10. CNT placed along the side of the AFM tip. 2
  • 3. The dexterity of the NanoBot system makes it fairly easy A loose bundle of CNTs can be used as a source insteadto align the CNT with respect to the AFM tip in XYZ. A of a substrate with grown CNTs. In this case, Van derreasonably well aligned CNT AFM tip (e.g., to ± 10º ) can Waals attraction is typically sufficient to attach a W tip, orbe made this way with some amount of practice. The CNT an AFM tip, to a selected CNT and pull it away from theis welded to the AFM tip using EBID of carbon. bundle.Cutting the CNT Away from the W tip Xidex CorporationAn electrical current pulse is then used to cut the CNT Xidex manufactures and sells the NanoBot system, anaway from the tungsten tip as shown in Figure 11. A easy-to-use, highly versatile, user-programmablespecialized software module included in the Action nanomanipulator built for use inside scanning electronToolbox provided with the NanoBot system allows microscopes (SEMs) and focused ion beam (FIB) tools.customers to cut CNTs in a controlled way, taking into The NanoBot transforms a SEM or FIB into a workshop foraccount different CNT sizes and lengths. The term nanodevice fabrication and testing.“Action” refers to an application-specific LabVIEW™based software module. Actions can be programmed Xidex Corporation was founded in 1997 as an Austin-either by Xidex’s application engineers or by the based Texas Corporation by Vladimir Mancevski,customer. President and Chief Technology Officer and Dr. Paul F. McClure, CEO. The company is wholly owned by its co- founders. W Tip NanoBot Sales AFM Tip CNT Tip For product inquiries please contact: Dr. Ray Eby Nanobiosystems, Inc. phone: 312-545-6527 e-mail: nanoray@sbcglobal.net Break Xidex Corporation 8906 Wall Street, Suite 703Figure 11. CNT separated from W tip. Austin, Texas 78754 phone: 512-339-0608Alternative Procedures fax: 512-339-9497Use of a sharp tungsten tip as an intermediate step, as e-mail: info@xidex.comdescribed above, facilitates selection and detachment of web: www.xidex.comthe CNT from its original substrate and also facilitatesattachment of the CNT to the AFM tip. Alternatively, a © 2011, Xidex Corporation. All rights reserved. NanoBot,CNT can be attached to an AFM tip in one step. However, Xidex, and the Xidex logo are trademarks of Xidexthis procedure may require more operator skill and can be Corporation. Other trademarks are property of theircomplicated by the presence of other CNTs in the vicinity respective owners. Product specifications andof the CNT selected for mounting. descriptions in this document are subject to change without notice.If additional batches of CNT tips need to be fabricated, 110313they can be mounted on the SEM sample holder byretracting and reinserting the load lock while the NanoBot Xidexcarrying the W tip remains in the sample chamber. Thisarrangement avoids the need to pump down the chambereach time a new batch of CNT AFM tips is to befabricated. NANODEVICES AT WORK 3