August 2007 The dream of being able to integrate multiple probes in an SPM system has finally become a reality. The integration of multiple probes in scanning probe microscopy (SPM) has been a researcher’s dream since its inception two decades ago. SPM systems use a stylus-like sensor to measure topography and certain functional properties, such as electrical, optical, thermal, and mechanical. There are a number of SPM systems currently on the market by companies such as Agilent, Santa Clara, Calif.; Horiba Jobin Yvon, Irvine, Calif.; WiTEC, Savoy, Ill.; and Asylum Research, Santa Barbara, Calif. However, only Nanonics Imaging Ltd., Jerusalem, Israel, currently manufactures an SPM system with independent scanning with up to four probes with ultra low noise and a variety of imaging modes. “Now as a result of the MultiView 4000 we have two and more hands that open new horizons in nanotechnology,” says Francesc Alsina of the Institut Catala de Nanotecnologia, Bellaterra, Spain. The benefits of having more than one probe range from surface resistivity measurements and optical or thermal desorption with multiple probes to excite and collect the desorbed species for chemical analysis, to nanoindentation with one probe with simultaneous and accurate atomic force microscopy (AFM), and/or thermal mapping using a second probe on polymeric, semiconductor, or other materials. Stefan Maier, at the Univ. of Bath, UK, says, “(having multiprobes) opens up new horizons in looking at the distribution of light in state of the art and future applications of nanophotonics.” According to David Lewis, manager of technical operations at Nanonics, “As the semiconductor industry reaches the 45 nm node along the path enunciated by Moore’s Law, there is no other technique available today to measure the electrical characteristics of such devices other than AFM-based multi-probe electrical measurements.” Lewis explains that light propagation in plasmonic waveguides and devices has to be characterized with pume-probe measurements where one probe excites a single plasmon with one optical probe and the other probe follows its propagation. This is also applicable in samples such as photonic band gap materials. Overcoming the bulk Giving legs to the the researchers’ dreams, Nanonics’ MultiView 4000 multi-probe SPM system allows two or more independently controlled SPM probes to be placed nanometers apart and enables a variety of multi point measurements on a nano scale. Until recently, this process was not possible as the probes of scanning mechanisms were bulky and awkward piezo scanners. The physical makeup of piezo scanners, when upright and side by side, prevents probes from getting close to one another. To solve this problem, Nanonics created the 3D FlatScan which is a planar, folded-piezo, flexure scan. The specialized glass-based probes of the scan can be as close as 10 nm and are capable of independently scanning each probe. Also, its ultra-thin design allows access either above or below the scanning stages. Furthermore, the scanner, which stands only 7 mm high, can be incorporated into systems where conventional scan stages are geometrically limiting. A variety of unique probes is available for the MultiView 4000. The system allows for next generation electrical/thermal characterization and imaging nanometric probe separations. Pump/probe near-field optical modes of imaging are standard, and nanofountain pens for chemical writing using a variety of inks are available with online ultrafine AFM topographic imaging. The specialized probes used with the MultiView 4000 consist of two platinum wires stretched through the nanopipette and are fused together at their tips. This fused junction has a resistance that is temperature-dependent. The probe allows simultaneous measurement of surface topography and thermal conductivity even in intermittent contact mode. With multiple probes, heat can be introduced at specific locations and detected at other locations. The probes also can be used for resistance measurements. With two cantilevered, near-field optical probes with exposed tips, optical pump/probe experiments can now be performed. As shown in the drawing above, light is injected through one probe and is guided through the fiber sample. With the second probe in place, the injected light can be collected and analyzed both spatially and temporally. Nanonics, now celebrating their 10th year, believes that the MultiView 4000 is having a major impact in the microscopy field. Alsina agrees, “The (MultiView 4000) is absolutely unique in the world of SPM. Through multiple innovations it has allowed researchers to enter a new realm of nanotechnology.” —Adria Nieswand