Compact Scanning Research Articles

Inelastic electron tunneling spectroscopy with a dilution refrigerator based scanning tunneling microscope

This paper presents the design and operations of a compact cryogenic scanning tunneling microscope system combined with a dilution refrigerator. We obtained a minimum temperature of 260 mK at the sample position. Taking advantage of low-temperature measurement for the spectroscopy, inelastic electron tunneling spectroscopy (IETS) at 4.4 K was demonstrated for the octanethiol molecules in a self-assembled monolayer. The spectrum showed many vibrational features as in the case of a high-resolution electron energy loss spectroscopy. We discuss the resolution of the IET signals focusing on its changes with the modulation voltage and the sample temperature. IETS at 260 mK is also presented with similar quality as in the case of 4.4 K, indicating that the vibration-dumping methods for the operation of the dilution refrigerator described in this paper are adequate.

A compact low temperature scanning tunneling microscope

We describe the design and fabrication of a compact Low Temperature Scanning Tunneling Microscope (LT-STM) together with a dipper cryostat for cooling the STM down to liquid helium temperatures. The STM, based on the piezo-tube walker as coarse approach mechanism, is suspended inside a cryostat vacuum can using three soft helical springs. The can is dipped into a liquid helium storage container for cooling the STM. Its compact size makes it less susceptible to mechanical vibrations and so the STM works with atomic resolution with a simple spring suspension. We demonstrate the performance of this STM for atomic resolution imaging and tunneling spectroscopy by observing the 3 ×3 charge modulation and the energy gap in the Charge Density Wave (CDW) phase of 2H-NbSe2 at liquid helium temperatures.

Sinusoidal fringe projection system based on compact and non-mechanical scanning low-coherence Michelson interferometer for three-dimensional shape measurement

We report a sinusoidal fringe projection system based on superluminiscent diode (SLD) as a broad-band light source in conjunction with an acousto-optic tunable filter (AOTF) as frequency tuning device for three-dimensional shape measurement. The present system is based on a compact low-coherence Michelson interferometer system. The conventional interferometric system was modified in which one side of the beam splitter was coated with aluminum oxide which is used as reference mirror. With this modified version, interference fringes can easily be obtained by simply placing the external mirror in contact on the other side of beam splitter. Sinusoidal fringes with multiple spatial-carrier frequency can be generated in real-time using the present system by means of changing the radio-frequency signal to AOTF electronically without mechanically moving any component in the system. The present system was tested by projecting the sinusoidal fringes on a step-like object and 3D shape of the object was reconstructed using Fourier transform fringe analysis technique. The main advantages of the proposed system are completely non-mechanical scanning, easy to align, high stability because of its nearly common-path geometry and compactness.

Targeted transfection of stem cells with sub-20 femtosecond laser pulses

Multiphoton microscopes have become important tools for non-contact sub-wavelength three-dimensional nanoprocessing of living biological specimens based on multiphoton ionization and plasma formation. Ultrashort laser pulses are required, however, dispersive effects limit the shortest pulse duration achievable at the focal plane. We report on a compact nonlinear laser scanning microscope with sub-20 femtosecond 75 MHz near infrared laser pulses for nanosurgery of human stem cells and two-photon high-resolution imaging. Single point illumination of the cell membrane was performed to induce a transient nanopore for the delivery of extracellular green fluorescent protein plasmids. Mean powers of less than 7 mW (<93 pJ) and low millisecond exposure times were found to be sufficient to transfect human pancreatic and salivary gland stem cells in these preliminary studies. Ultracompact sub-20 femtosecond laser microscopes may become optical tools for nanobiotechnology and nanomedicine including optical stem cell manipulation.

Development of a compact optical system for microarray scanning using a DVD pickup head

We present a compact optical system using a commercially available DVD pickup head for microarray scanning. Our instrument successfully provides a low-cost, compact, and simple microarray scanning optical system in comparison to conventional ones due to the use of small-sized optical components and the implementation of a simple autofocusing system using an embedded voice coil motor. The performance of this system was validated by using a microarray slide with spots of fluorescent dyes. It was confirmed that our optical head performed satisfactorily and was suitable for practical use in microarray scanners. This result provides evidence of the superiority of our microarray scanning optical system over conventional ones because of its space-saving properties and cost effectiveness.

A compact combined ultrahigh vacuum scanning tunnelling microscope (UHV STM) and near-field optical microscope

We have designed and constructed a hybrid scanning near-field optical microscope (SNOM)–scanning tunnelling microscope (STM) instrument which operates under ultrahigh vacuum (UHV) conditions. Indium tin oxide (ITO)-coated fibre-optic tips capable of high quality STM imaging and tunnelling spectroscopy are fabricated using a simple and reliable method which foregoes the electroless plating strategy previously employed by other groups. The fabrication process is reproducible, producing robust tips which may be exchanged under UHV conditions. We show that controlled contact with metal surfaces considerably enhances the STM imaging capabilities of fibre-optic tips. Light collection (from the cleaved back face of the ITO-coated fibre-optic tip) and optical alignment are facilitated by a simple two-lens arrangement where the in-vacuum collimation/collection lens may be adjusted using a slip-stick motor. A second in-air lens focuses the light (which emerges from the UHV system as a parallel beam) onto a cooled CCD spectrograph or photomultiplier tube. The application of the instrument to combined optical and electronic spectroscopy of Au and GaAs surfaces is discussed.

Water Vapor Profiling From CoSSIR Radiometric Measurements

Previous water vapor profiling by millimeterwave radiometry using the 183-GHz absorption line is generally limited to an altitude range of 0-11 km. The additional measurements at the frequencies of 380.2 0.8, 380.2 1.8, 380.2 3.3, and 380.2 6.2 GHz by the new airborne compact scanning submillimeterwave imaging radiometer (CoSSIR) reported in this paper can extend this profiling capability up to an altitude of about 15 km. This is demonstrated by recent CoSSIR measurements onboard the NASA WB-57 aircraft in a flight from Texas to Costa Rica on January 14, 2006. Retrievals of water vapor mixing ratio were performed at eight altitudes of 1, 3, 5, 7, 9, 11, 13, and 15 km from the CoSSIR data set acquired at observational angles of 0 and 53.4. The results were compared with other available measurements from near-concurrent satellites. A very good agreement was found between the collocated values of total precipitable water (TPW) derived from the CoSSIR-retrieved water vapor profiles and those estimated from Tropical Rainfall Measuring Mission Microwave Imager; the average TPW differences range between 0.30 and 0.64 cm, depending on CoSSIR's observational angles. The accuracy of the retrievals was inferred from an analysis of inflight CoSSIR radiometric signal fluctuations.

Eye-safe compact scanning LIDAR technology

A 1.5- μ m eye-safe, 3-D scanning, and compact Mie LIght Detection and Ranging (LIDAR) is presented. The transmitter of the LIDAR is based on a KTA optical parameter oscillator (OPO) resonator. For detecting return signals, an InGaAs APD is used. The all solid-state OPO laser transmitter has the feature of small volume and lightweight, which allows a 165-lb compact eye-safe scanning LIDAR to be constructed. A system simulation using our own model was conducted to direct the system development. A method to solve the problem with small active area APD detectors was developed and described. The preliminary field-test measurement results indicated that the LIDAR has the capability to detect aerosols and clouds in lower atmospheres up to three dimensions.

Stabilization of electron emission from nanoneedles with two dimensional graphene sheet structure in a high residual pressure region

A stable field emission (FE) under a high residual pressure (10−5Torr) was obtained by the thermal field operation of a nanoneedle cathode with a two dimensional graphene sheet structure. A high brightness electron emission of the order of 1012Asr−1m−2, as well as stable emission, was achieved. The performance of the stabilized cathode was demonstrated by the construction of a compact FE scanning electron microscope (SEM) system, and clear FE-SEM images were obtained at a residual pressure above 10−5Torr. The emission current fluctuation as a function of cathode temperature was discussed based on the Poisson distribution.

Development of compact field emission scanning electron microscope equipped with multiwalled carbon nanotube bundle cathode

As the first stage of development of a nanofocused x-ray source for high-resolution x-ray radiography, a commercial compact scanning electron microscope (SEM) was modified by replacing the thermionic cathode and two magnetic condenser lenses with a multiwalled carbon nanotube (MWCNT) bundle field emission (FE) cathode and a special designed Butler electrostatic lens, respectively. This modification also brought about a downsizing to the electron optical system, only 192mm of distance between the cathode and the sample stage was achieved. The MWCNT bundle FE cathode continuously emitted electrons for over 9h under a base pressure of ca. 10−5Torr which was a severer pressure for steady FE. The performance of electron gun system consisted of the MWCNT bundle FE cathode and the special Butler electrostatic lens was demonstrated by SEM images taken under the poor vacuum condition at room temperature.

A Compact and Versatile Scanning Tunnelling Microscope with High Energy Resolution for Use in a 3He Cryostat

We present a simple design for a very-low temperature STM for the investigation of mesoscopic superconductors. The nonmagnetic microscope operates in a conventional 3He cryostat at T = 240 mK and in magnetic fields up to B = 1 T. Efficient filtering of all electrical lines at base temperature results in a voltage resolution ≈ 20μ V, which has been tested by measuring the differential conductance of superconducting aluminium. The successful operation in magnetic field is demonstrated by spectroscopy on superconducting aluminium as well as by demonstrating atomic resolution of HOPG.

3D metrology with a compact scanning probe microscope based on self-sensing cantilever probes

The key element of a scanning force microscope (SFM) is the cantilever probe. Commonly, its deflection is measured using either an optical lever or interferometric methods. However, optical detection methods increase the complexity of the microscope set-up and restrict its application in difficult environments. By integrating the detection system on the cantilever chip itself, the microscope becomes easier to implement and use. Integrated systems have been realized based upon piezoelectric, piezoresistive and capacitive methods. In the present work self-sensing piezoresistive cantilevers have been used. For these probes a very compact SFM unit has been developed based upon a novel chip holder, which allows simultaneous fixing of the chip and contacting of the piezoresistive sensor electrodes. This compact unit can be tilted to perform investigations on three-dimensional structures not feasible with conventional scanning force microscopes. As an example of a 3D application, measurements on a 100 µm ruby sphere are presented.

Optimized System Design and Construction of a Compact Whole-hand Scanner for Diagnosis of Rheumatoid Arthritis

We have developed a compact magnetic resonance (MR) imaging scanner with permanent magnet, gradient coil set, and radiofrequency (RF) coils optimized for whole-hand examination for the diagnosis of rheumatoid arthritis (RA). The system weighs about 600 kg, and installation space is 2 m(2), excluding the shield room. Hand examinations of normal volunteers and patients with RA were performed using a 3D T(1)-weighted gradient-echo (GRE) sequence and short T(I) inversion recovery 3D fast spin-echo (STIR-3DFSE) sequence, and anatomical structures and various lesions of the hand caused by RA were clearly visualized in a 16-min examination. It was concluded that the system could be used for diagnosis of RA in even a small clinic.

Ferromagnetic shape memory microscanner system for automotive applications

A microscanner system for optical sensing of angle and distance is presented, which is controlled by a ferromagnetic shape memory (FSMA) microactuator. The main features of the FSMA microactuator are a large scanning angle up to 60 deg and a large bandwidth of frequencies given by a broad off-resonance regime below the thermal cut-off frequency at about 120 Hz and the resonance regime between 160 and 220 Hz. The small size and low mass of the FSMA microactuator allows the design of a very compact and robust scanner system, which enables new portable and mobile applications. In this paper, the sensing of objects in road traffic is pursued as an application in the automotive field, which requires small moving masses being insensitive to vibrations and shock. The main components of the microscanner system are the FSMA microactuator, a pulsed laser diode, an integrated angle sensor, an avalanche diode and a time-of-flight measurement setup for distance acquisition. The maximum scanning range of the first prototype is about 30 m for cooperative (reflecting) objects. The angular resolution is about 0.5 ◦ .

Compact design of a low temperature XY stage scanning tunneling microscope

We describe the design and development of a compact low temperature XY stage scanning tunneling microscope dedicated to operation at low temperatures, in high magnetic fields, and in an ultrahigh vacuum environment. The system features a homemade compact scanning tunneling microscope (STM) head coupled to an inertially driven horizontal slider which allows a two-dimensional coarse positioning of the tip over 6×3mm2 with submicronic resolution. We also describe the geometry used to avoid coupling between the three-dimensional coarse and fine movements. To demonstrate the mechanical stability of the STM we display atomic resolution and large scale imaging. We illustrate the capabilities of our system by performing scanning tunneling spectroscopy on PbMo6S8 microcrystals.

A compact dual-tip STM design

A compact dual-tip scanning tunneling microscope (STM) design that achieves both rigidity and stability is presented. We constructed a prototype unit to perform tests in ambient conditions. The two STM tips were able to maintain a stable tunneling condition with the sample surface simultaneously. Topographic images of a fresh cleaved graphite were taken simultaneously from the two tips. A common feature found in both images indicates that the two tunneling spots are ~800 nm apart

A Multiband, Compact, and Full-Duplex Beam Scanning Antenna Transceiver System Operating From 10 to 35 GHz

This paper presents a compact phased-array antenna transceiver system that can operate over a wide bandwidth from 10 to 35 GHz with the abilities of beam scanning and full-duplex communication. The system consists of ultrawide-band Vivaldi antennas, a multiline PET-based phase shifter, a six-channel microstrip multiplexer, and monolithic microwave integrated circuit (MMIC) amplifiers. The multiplexer routes 10, 19, and 32 GHz signals to the transmit path and 12, 21, and 35 GHz signals to the receive path. The multiplexer shows insertion loss between 2.2 and 3.4 dB for all six channels and together with wide-band MMIC amplifiers plays an important role to build a compact, multifrequency, and full-duplex transceiver system. The system should have many applications in multiband satellite communication systems and radar systems.

67.3: Progress in Small-Form-Factor Lasers for Projection Displays

Prospects of red, green and blue lasers as light source for laser displays are discussed. Recent progress on semiconductor based red, green and blue lasers may enable very compact scanning beam laser displays for mobile applications. For larger screen displays, lasers are employed as illumination source for imager based projection engines.

Holographic optical elements as scanning lidar telescopes

We have developed and investigated the use of holographic optical elements (HOEs) and holographic transmission gratings for scanning lidar telescopes. Rotating a flat HOE in its own plane with the focal spot on the rotation axis makes a very simple and compact conical scanning telescope. We developed transmission and reflection HOEs for use at the first three harmonic wavelengths of Nd:YAG lasers. The diffraction efficiency, diffraction angle, focal length, focal spot size and optical losses were measured for several HOEs and holographic gratings, and found to be suitable for use as lidar receiver telescopes, and in many cases could also serve as the final collimating and beam steering optic for the laser transmitter. Two lidar systems based on this technology have been designed, built, and successfully tested in atmospheric science applications. This technology will enable future spaceborne lidar missions by significantly lowering the size, weight, power requirement and cost of a large aperture, narrow field of view scanning telescope.

Teaching Medical Students Diagnostic Sonography

The purpose of this pilot project was to train medical students in sonography. Thirty-three medical students participated in a pilot sonography course, which included exposure to ultrasound physics, knobology of a compact ultrasound scanner, training in scanning and anatomy of the aorta and right kidney, and reading assignments in these areas. Pretraining and posttraining examinations were given in these areas to analyze the degree of knowledge gained by these methods. Nearly all of the medical students increased their basic knowledge of sonography and improved their scanning skills. The improvement was statistically significant in all areas. Training in sonography for medical students could be used as a foundation for later, more specialty-specific training to improve the overall medical sonography skills for all physicians.