The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a "nanostressing stage" located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer ("sword-in-sheath" failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.

We report the results of an experimental study of the correlations between line edge roughness (LER) and aerial image contrast for different lithographies in identical processing conditions. The characterization has been performed using atomic force microscopy carbon nanotube tips to image the top and bottom of trenches with very high resolution. Experimental results generally support that higher aerial image contrast leads to lower line edge roughness, but differences exist among the lithographies and resists. Top surface roughness results show similar trends with LER. Higher aerial image modulation also yields higher resist sidewall angle.

The resolution and wear properties of carbon nanotube and etched-silicon atomic force microscopy probes are compared in intermittent-contact mode. Carbon nanotube probes have at least 20 times the life of etched-silicon probes and provide better resolution at all stages. Sample wear is minimized with carbon nanotube probes. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1452782͔Since the discovery of carbon nanotubes ͑CNTs͒ in 1991, 1 much has been done to characterize their properties and explore their potential applications. Although many of these potential uses are still in the nascent stage, it has become clear that CNTs, because of their geometry and unique mechanical properties, are very well suited for scannedprobe microscopy probes, 2 in particular atomic-force microscopy ͑AFM͒, 3 but also magnetic-force microscopy 4 and electric-force microscopy. 5 CNTs are preferred probes for topographic imaging because they ͑1͒ provide improved resolution ͑uniformly good end form͒, ͑2͒ allow investigating deep and/or narrow surface features ͑very high aspect ratio and long length͒, ͑3͒ enable probing sensitive and/or easily damaged surface features ͑mechanical properties of the CNT͒, ͑4͒ have long life ͑anecdotal evidence of a factor of 10 increased life without degradation of resolution͒, and ͑5͒ provide enhanced capabilities for scanning in water ͑hydro-phobicity of the CNT͒. 6 In this letter we quantify the improved resolution, the long life and the superior imaging properties of CNT probes on fragile samples. We compare the wear and degradation of conventional commercial etched-silicon ͑ES͒ probes with those of multiwall CNTs during intermittent-contact imaging. We confirm at least an order of magnitude longer life of the CNT without degradation of resolution; in fact we are not able to find a reduction of resolution or any wear of the CNT even after more than two meters of scanning ͑over 1000 2 mϫ2 m images͒. Samples imaged with CNT probes also show negligible wear compared with those imaged with ES probes. Figure 1 shows a comparison of the resolution achievable with CNT ͑a͒ and ES ͑b͒ tips, using 10 nm Co spheres on Si͑111͒. The end form of tips made from multiwall CNTs or CNT bundles is invariably better than 20 nm in diameter, and can be made as small as 3 nm, providing resolution of this order. Although new ES tips can sometimes achieve the resolution of a CNT ͑we have never observed it to be better than that of a CNT͒, their resolution begins to degrade within two or three scans in most cases. Figure 1 also shows a comparison of the ability of the CNT tips to probe deep features ͑c͒ versus that of an ES tip ͑d͒. Because they are long, narrow tubes, CNTs have a high aspect ratio ͑tubes with lengths from nanometers to several micrometers can be fabricated as metrology probes͒. Conventional ͑ES͒ probes have a pyramidal shape, which is apparent in the AFM image of a deep trench. Thus, CNT probes can profile morphologies that are inaccessible to ES probes.The wear characteristics of conventional ES tips ...

Conductivity measurements reflect vortex solid melting in YBa 2 Cu 3 O 72d films. Field-independent glass exponents n g Ӎ 1.9 and z g Ӎ 4.0 describe the transition T g ͑H͒ for 0 , H # 26 T. At low fields, 3D XY exponents n XY Ӎ 0.63 and z XY Ӎ 1.25 are also observed, with z XY smaller than expected. These compete with glass scaling according to multicritical theory. A predicted power-law form of T g ͑H͒ is observed for 0.5T c , T g , T c . For T g , 0.5T c , 3D XY scaling fails, but a selfconsistent lowest Landau level analysis becomes possible, obtaining T c2 ͑H͒ with positive curvature.[S0031-9007(97)02912-8] PACS numbers: 74.25.Bt, 74.25.Dw, 74.40. + k, The nature of fluctuations near the superconducting to normal state transition in high-temperature superconductors (HTSCs) is still a matter of controversy. Several distinct fluctuation types and regions have been proposed, e.g., 3D XY fluctuations at low fields, lowest Landau level (LLL) fluctuations at high fields, and glasslike fluctuations (for disordered HTSCs) near the finite-field transition T g ͑H͒. However, experimental analyses based upon the different scaling theories lead to conflicting results. This situation is most evident for competing 3D XY and LLL fluctuations, both of which are supported experimentally, in the same region of the phase diagram, in spite of being incompatible [1].The 3D XY transition is driven by phase fluctuations of a complex order parameter (OP) which fall into the universality class of the l transition in 4 He. The zerofield, "intermediate" (nonelectrodynamic) phase fluctuations of the HTSCs are thought to be of this type [2]. At T T c (and H 0), these fluctuations diverge in size, driving the resistive phase transition. Recent experimental evidence supporting this picture is found in specific heat [3,4], magnetization [4,5], penetration depth [6], and current-voltage (J-E) measurements [4,7]. The finite-field transition T g ͑H͒, which is similarly driven by phase fluctuations of the OP, joins smoothly to T c ϵ T g ͑H 0͒. However, the glass and 3D XY fluctuations exhibit distinct scaling functions and exponents [2].Fluctuations of the OP amplitude occur near the upper critical (mean-field) temperature T c2 ͑H͒. These fluctuations drive the Cooper pair density to zero, but do not correspond to a true transition; superconducting order vanishes at the slightly lower temperature T g ͑H͒. In the lowfield region, the distinction between OP amplitude and phase fluctuations results in the dominance of 3D XY critical behavior near T T c . At high fields, this distinction is not present, yielding a different type of behavior, most conveniently described in terms of the Ginzburg-Landau LLL approximation, with its corresponding scaling theory [8,9]. Experimental evidence in support of this behavior is found in specific heat [10 -12], magnetization [10,12], and J-E characteristics [10,13]. A crossover is expected between the low-field (3D XY ) and high-field (LLL) behaviors, and its clarification is fundamental in the investigation of H...

The magnetic domain structures on the {110} plane of magnetite (Fe3O4) below the Verwey transition (Tv=120K) were studied using a Low‐Temperature Magnetic Force Microscope (LTMFM). At 298K, domain structures consisted of arrays of 180°, 109° and 71° walls, typical for magnetite with cubic anisotropy. At 77K (below Tv), the cubic style patterns disappeared and transformed into uniaxial patterns consistent with the uniaxial magnetocrystalline symmetry of the low‐temperature monoclinic phase of magnetite. We also observed two distinct styles of domain patterns below Tv: (1) wide domains separated by straight 180° walls along the in‐plane [100] easy axis; and (2) intricate wavy walls with reverse spike domains characteristic of out‐of‐plane easy axes. This intimate mixture of domain styles within adjacent areas of the crystal reflects variations in the direction of the magnetic easy axes in different regions produced by c‐axis twinning of the crystal below Tv The thermal dependence of planar and wavy‐wall patterns show little change from 77K until 110K, where patterns disappear. Upon cooling back to 77K, domain structures are different from the initial 77K states, indicating that renucleation of different domain states occurs by cycling near Tv.