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A combined atomic force microscope (AFM) and scanning near-field optical microscope (SNOM) has been constructed to obtain images under liquids. In this combined AFM-SNOM an inverted ac mode configuration is used where the AFM cantilever is driven by exciting acoustic modes of the liquid cell. Optical images of latex spheres on a cantilever have been obtained under perfluorononane, butanol, and water with a lateral resolution of 100 nm. Fluorescence images of latex spheres have been obtained under perfluorononane. The ability to image under liquids opens up a wide range of applications of near field optical microscopy in chemistry and biology.

Near‐field imaging is a means of exceeding the diffraction limit in optical microscopy to yield subwavelength resolution optical images of a sample surface. In order to achieve such high resolution, it is necessary to scan the measurement probe above the surface at a height of only a few nanometers which requires careful control of the separation between tip and sample. In the implementation of the near‐field optical microscope (NFOM) reported here, the distance regulation scheme is based on an inverted noncontact atomic force microscope (AFM) in which a cantilever is used as the sample substrate and imaging is performed with a fiber optic tip. In this way, both the benefits of AFM and NFOM are realized simultaneously.

We describe a highly sensitive new type of calorimeter based on the deflection of a ‘‘bimetallic’’ micromechanical sensor as a function of temperature. The temperature changes can be due to ambient changes, giving a temperature sensor or, more importantly, due to the heat absorbed by a coating on the sensor, giving a heat sensor. As an example we show the results of using the sensor as a photothermal spectrometer. The small dimensions and low thermal mass of the sensor make it highly sensitive and we demonstrate a sensitivity of roughly 100 pW. By applying a simple model of the system the ultimate sensitivity is expected to be of the order of 10 pW. The thermal response time of the cantilever can also be determined, giving an estimate of the minimum detectable energy of the sensor. This we find to be 150 fJ and again from our model, expect a minimum value of the order of 20 fJ.

High performance improvement (+88% in peak Gm and >30% in linear and saturation region drain currents) was observed for N-MOSFETs with Oxygen-Inserted (OI) Si channel. From TCAD analysis of the C-V measurement data, the improvement was confirmed to be due to electron mobility enhancement of the OI Si channel (+75% at Ninv = 4.0 × 1012 cm−2 and +25% at Ninv = 8.0 × 1012 cm−2). Raman and high-resolution Rutherford backscattering measurements confirmed that negligible strain is induced in the OI Si layer, and hence, it cannot be used to explain the origin of mobility improvement. Poisson-Schrodinger based quantum mechanical simulation was performed, taking into account phonon, surface roughness and Coulomb scatterings. The OI layer was modeled as a “quasi barrier” region with reference to the Si conduction band edge to confine inversion electrons. Simulation explains the measured electron mobility enhancement as the confinement effect of inversion electrons while the formation of an super-steep retrograde we...

We have investigated the quantification properties of scanning capacitance microscopy (SCM) by using two dedicated test structures and highlight the response of SCM to changes in dopant density. Our results indicate that contrast reversal occurs and that the SCM output is not always a monotonically increasing signal with decreasing dopant density. Two epitaxially grown staircase structures covering the doping ranges 1014–1020 cm−3 p type and 5×1014–5×1019 cm−3 n type were produced for this study as the turning point in the response function typically occurs at a doping level of around 1017 cm−3. Through the use of a simple simulation model we see that contrast reversal is expected due to a relative shift between the dC/dV curves for different doping levels. The onset of contrast reversal can be adjusted by changing the dc sample bias leading to a shift in the operating position of the SCM, and the significance of this point will be discussed here.

A near‐field optical microscope (NFOM) has been developed that combines the features of a near‐field optical microscope and an atomic force microscope. Improved control over tip‐sample separation has led to improved optical imaging and independent surface topography information. The tip oscillation is normal to the sample plane thereby reducing lateral forces—important for nonperturbative imaging of soft samples. Both topographic images and reflection near‐field optical images are presented which demonstrate the capability of the system.

The asymptotic behavior of the pair correlation ω2(r) = 〈σ0σr〉 between two spins at sites 0 and r on an axis of an isotropic antiferromagnetic triangular lattice is investigated with the aid of the theory of Toeplitz determinants as developed by Wu. The leading terms in the asymptotic expansion are obtained for large spin separation at fixed nonzero temperature. Evidence is presented that the zero‐point behavior of the correlation is of the form ω2(r) ∼ e0r−½ cos ⅔πr, where r = |r| is the spin separation and e0=212(E0T)2=0.632226080…,E0T being the decay amplitude of the pair correlation at the Curie point (critical point) of an isotropic ferromagnetic triangular lattice. A special class of fourth‐order correlations ω4(r) = 〈σ0σδσr σr+δ〉 − 〈σ0σδ〉 〈σrσr+δ〉 between the four spins at sites 0, δ, r, and r + δ on the same lattice axis, where δ is a lattice vector, is reconsidered. The asymptotic form of the correlation for large separation of pairs of spins r = |r| is obtained for all fixed temperatures.

A class of fourth‐order spin correlations whose sum is closely related to the specific heat is calculated exactly by Pfaffian perturbation theory. In the particular case when the four spins lie on a lattice axis, it is shown that the reduced fourth‐order correlation function has the asymptotic form 〈σ0, 0σ1, 1σk, kσk+1, k+1〉−〈σ0, 0σ1, 1〉 〈σk, kσk+1, k+1〉≏A′(e−2βk/k2), where β−1 is the (positive) mean range of order. The decay of correlations with spin separation k is symmetric about the critical point β = 0. The amplitude A′ is 1/π2 at the critical point and is 1/(2π) at all other temperatures. Correlations on ferro‐ and antiferromagnetic triangular and quadratic lattices are discussed in some detail.

A Pfaffian representation, of the partition function of the triangular lattice is used to derive expressions for various two, four, and six spin correlations in terms of Pfaffians. The pair correlations along a diagonal are expressed as a Toeplitz determinant whose limiting form yields the spontaneous magnetization. At the ferromagnetic critical point the correlations decay as 1/r12 with approximately radial symmetry. At the antiferromagnetic zero point the ground state is highly degenerate—it has finite entropy—and on a given sublattice the pair correlations along a row decay as e/r12, where e=+e0 on the sublattice containing the origin spin and e≃−12e0 on the other two sublattices. Finally, the perpendicular susceptibility, χ⊥, which depends on a finite number of correlations, is calculated; its ferromagnetic behavior is similar to that of the perpendicular susceptibilities of the quadratic and honeycomb lattices, but for an antiferromagnet χ⊥ diverges as 1/T at low temperatures.

A detailed discussion of pair correlations ω2(r) = 〈σ0σr〉 between spins at lattice sites 0 and r on the axes of anisotropic triangular lattices is given. The asymptotic behavior of ω2(r) for large spin separation is obtained for ferromagnetic and antiferromagnetic lattices. The axial pair correlation for the ferromagnetic triangular lattice has the same qualitative behavior as that for the ferromagnetic rectangular lattice: There is long‐range order below the Curie point TC and short‐range order above. It is shown that correlations on the anisotropic antiferromagnetic triangular lattice must be given separate treatment in three different temperature ranges. Below the Neel point TN (antiferromagnetic critical point), the completely anisotropic lattice exhibits antiferromagnetic long‐range order along the two lattice axes with the strongest interactions. Spins along the third axis with the weakest interaction are ordered ferromagnetically. Between TN and a uniquely located temperature TD, there is antiferro...

A general argument is presented that a change in the nature of the short‐range order will occur above a precisely located temperature TD, the disorder point, for a class of magnetic models. The possibility of detecting a disorder point by neutron scattering is investigated by calculating the relative scattering intensity for a one‐dimensional model.

The partition function and spin pair correlation functions have been calculated exactly for a classical linear chain model with alternate next‐nearest‐neighbor (nnn) interactions, in which the interaction energies between pairs of nearest (nn) and next‐nearest (nnn) neighbor spins are arbitrary functions of the angles between the relevant spins. Of special interest is the cosine interaction model described by the Hamiltonian H=−ΣNi=1[J1(cosϑ2i−1,2i +cosϑ2i,2i+1)+J2cosϑ2i−1,2i+1]. When the nnn interaction is antiferromagnetic (J2