Size effect on the kinematic parameters of nanometer-thick bilayer films

The behavior of nanodimensional bilayer structures (plates) of finite length consisting of nanometer-thick crystalline Ni and Cu films has been studied by means of molecular dynamics simulation. The inter-atomic interactions were described within the framework of the embedded atom method. It is shown that, in the absence of an external action, the nanostructures perform mechanical oscillations with the amplitude and frequency determined by the length and thickness of the plate. The dependence of the parameters of oscillations of the nanodimensional structures on their dimensions is established. The results can be used in designing components of nanodevices for various applications.     

Effects of nanometer-thick passivation layers on the mechanical response of thin gold films

The mechanical behavior of freestanding gold membranes 0.5 micron thick with and without passivation layers was studied with a membrane deflection experiment. Membrane width was varied from 2.5 to 20 microns to investigate size effects. The presence of the passivation layer had the effect of reducing the membrane strength. Yield stress, as well as fracture strain and stress, were all found to be significantly lower for the passivated specimens. The residual stress state was found to be significantly larger with passivation, to the degree of generating prestressed cracks at micromachined notches. Membrane width had the greatest effect on the residual stress state with smaller widths having larger residual stress.     

Absolute high spectral resolution measurements of surface solar radiation for detection of water vapour continuum absorption

Solar-pointing Fourier transform infrared (FTIR) spectroscopy offers the capability to measure both the fine scale and broadband spectral structure of atmospheric transmission simultaneously across wide spectral regions. It is therefore suited to the study of both water vapour monomer and continuum absorption behaviours. However, in order to properly address this issue, it is necessary to radiatively calibrate the FTIR instrument response. A solar-pointing high-resolution FTIR spectrometer was deployed as part of the 'Continuum Absorption by Visible and Infrared radiation and its Atmospheric Relevance' (CAVIAR) consortium project. This paper describes the radiative calibration process using an ultra-high-temperature blackbody and the consideration of the related influence factors. The result is a radiatively calibrated measurement of the solar irradiation at the ground across the IR region from 2000 to 10?000?cm(-1) with an uncertainty of between 3.3 and 5.9 per cent. This measurement is shown to be in good general agreement with a radiative-transfer model. The results from the CAVIAR field measurements are being used in ongoing studies of atmospheric absorbers, in particular the water vapour continuum.     

Intensity of the absorption lines of spin wave resonance modes in garnet films with nanometer-thick pinning layers

We have studied the influence of the thickness of the spin-pinning layer on the intensity of spin wave resonance (SWR) modes in two-layer garnet ferrite films. For pinning layers with thicknesses in the nanometer range, the SWR mode absorption lines exhibit periodic variations for a certain orientation of the magnetic field relative to the film plane. At thicknesses equal to a quarter of the wavelength of the spin wave in the pinning layer, the intensity of SWR mode absorption lines exhibits a sharp (approximately 3.5-fold) increase.     

Absolute cryogenic radiometer for high-current photometric measurements

A cryogenic radiometer with electrical substitution has been developed for precise photometric measurements. The radiometer design and specifications are described. The radiometer has an accuracy of 0.02%. Its main use is to calibrate the spectral response of reference radiometers. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 22–25, November, 1996.     

Absolute figure measurements with a liquid-flat reference

We describe a variation of the liquid-flat technique fordetermining the absolute flatness of a 240-mm-diameter optical surfaceto an accuracy better than 1/100lambda in both its horizontal(three-point support) and vertical orientations. Using theappropriate mathematics to calculate the surface deformation of a diskdue to gravity, we achieved verification of the method by comparingmeasurements carried out on a pair of optical flats and a liquidreference surface.     

Absolute solar transmittance interferometer for ground-based measurements

The absolute solar transmittance interferometer measures absolute solar radiance at the Earth's surface. The instrument is based on a Fourier-transform spectrometer that utilizes a liquid-nitrogen-cooled InSb detector and appropriate optical bandpass filters. The recorded solar spectra are calibrated against National Institute of Standards and Technology traceable lamps and a blackbody source. The spectral range addressed by this instrument is from 1950 to 10100 cm(-1) at a resolution of 2 cm(-1). The optical design of the instrument and the experimental methods are discussed. A discussion of the uncertainties involving the instrument and the calibration sources is presented. Initial measurements from several sites are compared with atmospheric model calculations.     

Intermodulation measurements in YBaCuO films

A technique for measuring the intermodulation signal arising in a nonlinear high-temperature superconductor film is suggested. Using a one-port resonator, the technique significantly increases sensitivity of the measuring system as compared to that of a two-port-resonator design. Specifically, it lowers the minimum measurable power at a given magnetic field strength on the film surface. Measurements of the intermodulation signal power as a function of the input power for YBaCuO films differing in surface resistance and thickness are reported. Based on the measured data, the intermodulation characteristic magnetic field is computed. The quantity characterizes nonlinear film properties of the regardless of the measuring system employed.     

Absolute frequency measurements of lasers in submillimeter and infrared ranges

Conclusion The investigations into lasers constructed in the submillimeter and infrared regions showed satisfactory results for their use in absolute frequency measurements. The fast-response nonlinear elements — W=Si and W=Ni point diodes — have been tested in the multiplier-mixer mode from 337 to 10 exclusively. The frequencies have been measured of the molecular lasers HCN (=337 ), D₂O (=84 ), H₂O (=28 ) and the P(14) CO₂ (=10.53 ) and R(30) (=10.18 ) lines. The measurement error of 5·10^–7 was determined by the indeterminacies of fixing the peak of the laser generation lines. An increase of the measurement accuracy will be achieved by the mutual tying in of the laser frequencies to one another.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 59–61, October, 1976.     

Absolute linearity measurements on LiTaO3 pyroelectric detectors

The nonlinearity characteristics of a number of LiTaO3 pyroelectric detectors were experimentally investigated using the National Physical Laboratory (NPL) detector linearity characterization facility. All the detectors examined were shown to exhibit a superlinear response, i.e., the responsivity of the detectors increases as the incident radiant power increases. The temperature coefficient of response of some of these LiTaO3 pyroelectric detectors was measured and found to be approximately +0.2% degrees C(-1). The superlinear behavior of the LiTaO3 pyroelectric detectors was attributed to the positive temperature coefficient of response values of these detectors. Moreover, the linearity factor of gold-black-coated LiTaO3 pyroelectric detectors was shown to exhibit a dependency on the area of the spot illuminating the active area of the detector, i.e., on the incident irradiance. Possible reasons for the observed behavior are proposed and discussed. Some variations in the slopes of the plots of the linearity factor versus irradiance for different areas being illuminated have been assigned to the poor spatial uniformity of response of these detectors.     

Absolute linearity measurements on a PbS detector in the infrared

The nonlinearity characteristics of a commercially available thin-film photoconductive PbS detector were experimentally investigated in the infrared using the National Physical Laboratory detector linearity characterization facility. The deviation from linearity of this detector was shown to be significant even for relatively low values of radiant power incident on the active area of the detector. For example, the linearity factor was approximately 0.8 when 0.6 microW of radiant power at a wavelength of 2.2 microm was illuminating a spot of 1 mm in diameter on the active area of the PbS detector. These figures demonstrate the poor linearity characteristics of this detector and provide a warning to other users of PbS detection systems. The deviation from linearity was shown to be a function of the size of the spot being illuminated on the detector active area, as well as the wavelength of the incident radiation. The deviation from linearity was shown to be a function of irradiance illuminating the detector for irradiance values lower than 1 microW mm(-2).     

Absolute infrared absorption measurements in optical coatings using mirage detection

Absolute measurements of the optical absorption at λ=10.6 μm of BaF₂ thin film grown on a ZnSe substrate and bare ZnSe substrate surface were performed by collinear photothermal deflection technique. Absorption values were obtained in an absolute manner by fitting experimental data to the theoretical expressions of beam deflection for two particular cases: when thermal wave extends far from the laser spot and the opposite, when the heated region does not stretch beyond the laser spot. The validity of the theoretical models were tested in the range of modulation frequencies from 20 Hz to 2700 Hz. This method was also applied to the analysis of fused silica and sapphire bulk samples in order to be used as reference absorbing media in the infrared spectral range. Optical absorption of BaF₂ thin film and ZnSe substrate surface were also deduced from the same theoretical approach using sapphire as a bulk reference medium. From both calculation methods an absorptance of 1200 ppm for BaF₂ thin film and of 425 ppm for ZnSe plate surface were measured.     

Hardness measurements of thin films

A simple technique is presented to obtain the characteristic microhardness values of surface coatings that are too thin for the values to be directly measured. The application of the technique requires conventional microhardness measurements on both coated and uncoated substrates and a knowledge of the film thickness. The film hardness is obtained from these data by the use of a simple formula which is based on a physical model of film deformation during indentation. The model is verified for chromium films on four different substrate materials. Hardness values of the film material can be obtained from films with a thickness of more than 2000 Å with this technique.     

Absolute linearity measurements on HgCdTe detectors in the infrared region

The nonlinearity characteristics of photoconductive and photovoltaic HgCdTe detectors were experimentally investigated in the infrared wavelength region by use of the National Physical Laboratory detector linearity measurement facility. The nonlinearity of photoconductive HgCdTe detectors was shown to be a function of irradiance rather than the total radiant power incident on the detector. Photoconductive HgCdTe detectors supplied by different vendors were shown to have similar linearity characteristics for wavelengths around 10 microm. However, the nonlinearity of response of a photovoltaic HgCdTe detector was shown to be significantly lower than the corresponding value for photoconductive HgCdTe detectors at the same wavelength.     

The great advances in radiation measurements

The title of this banquet talk was selected to entertain conferees with recollections of major advances in dosimetry that have stimulated appetites for scientific progress. Recalling over fifty years of use of dosimetric instruments and concepts in the 1950-2000 era leads to an appreciation of many advances in solid state dosimetry, which others here know well and pursue vigorously. This author has been mainly a user, admirer, and interpreter of the fundamental methods of dose measurement. These advances have allowed ease of application in radiation protection and medical physics, for determining current routine and accidental exposures to workers, and for precise radiotherapeutic dose delivery. In more recent years, advances in identifying means of locating selective depositions of energy in various materials are providing ways of retrospectively assessing doses to tissue that were deposited many years ago. These methods also will allow development of quantitative theories of radiation damage once the lesions of interest are identified through further advances in molecular genetics. Yet, reflections on the past fifty years lead to increasing appreciation of the enormous achievements of our predecessors in the 1900-1950 period. Therefore, this presentation emphasises methods used by the author and some of his data interpretations during his 52 year career, with somc examination of the earlier origin of some of these methods.