Arthur E. Dixon

Reflected-light, photoluminescence and OBIC imaging of solar cells using a confocal scanning laser MACROscope/microscope

Abstract This paper describes a confocal scanning beam MACROscope/Microscope which can image specimens up to 7 × 7 cm in size using reflected light, photoluminescence and optical beam induced current. The MACROscope provides a 10 μm spot size at various wavelengths and generates 512 × 512 pixel images in less than 5 s. When used in combination with a conventional confocal scanning laser microscope sub-micron spot sizes become possible providing resolutions as high as 0.25 μm laterally and 0.5 μm axially in reflected light. The main function of this imaging system is to spatially resolve any defects within solar cells and similar devices. Several reflected-light, photoluminescence and OBIC images of CdS CuInSe 2 and CdZnS CuInSe 2 thin film solar cells are presented.

Photoluminescence imaging of porous silicon using a confocal scanning laser macroscope/microscope

This letter describes a confocal scanning beam macroscope/microscope that can image specimens up to 7 cm in diameter using both photoluminescence and reflected light. The macroscope generates digital images (512×512 pixels) with a maximum 5 μm lateral resolution and 200 μm axial resolution in under 5 s, and in combination with a conventional confocal scanning laser microscope can provide quality control at a macroscopic/microscopic level for porous silicon specimens, wafers, detectors, and similar devices. This combination of instruments can also be used as a method for evaluating preparation parameters involved in the manufacture of porous silicon. Various confocal and nonconfocal photoluminescence and reflected‐light images of porous silicon are shown using both a macroscope and a conventional confocal scanning laser microscope. A 3D profile of a porous silicon structure reconstructed from confocal slices is also shown.

A new confocal scanning beam laser MACROscope using a telecentric, f‐theta laser scan lens

A new confocal scanning beam system (MACROscope) that images very large‐area specimens is described. The MACROscope uses a telecentric, f‐theta laser scan lens as an objective lens to image specimens as large as 7·5 cm × 7·5 cm in 5 s. The lateral resolution of the MACROscope is 5 μm and the axial resolution is 200 μm. When combined with a confocal microscope, a new hybrid imaging system is produced that uses the advantages of small‐area, high‐speed, high‐resolution microscopy (0·2 μm lateral and 0·4 μm axial resolution) with the large‐area, high‐speed, good‐resolution imaging of the MACROscope. The advantages of the microscope/MACROscope are illustrated in applications which include reflected‐light confocal images of biological specimens, DNA sequencing gels, latent fingerprints and photoluminescence imaging of porous silicon.

Characterization of the anomalous second junction in Mo/CuInSe2/(CdZn)S/ITO solar cells

Abstract In general any analysis of Mo/CuInSe 2 /(CdZn)S/ITO thin film solar cells assumes that the contacts to CuInSe 2 and to (CdZn)S are ohmic. Current-voltage analysis has shown the presence of a second junction in these devices. The Mo/CuInSe 2 interface was investigated as the possible location for this second junction. A scanning laser microscope with a cold stage was used to probe different regions of these devices as a function of temperature. Special devices with a transparent molybdenum back contact 400 A thick were used to allow direct probing of the Mo/CuInSe 2 interface through the molybdenum. The results show that a second junction exists at the Mo/CuInSe 2 interface. The J-V curves for this junction as a function of temperature have been extracted from the characteristic curves of the complete device and have been accurately modeled using theory developed for quasi-ohmic contacts.

A scanning beam time-resolved imaging system for fingerprint detection.

A highly sensitive confocal scanning-beam system for time-resolved imaging of fingerprints is described. Time-resolved imaging is a relatively new forensic procedure for the detection and imaging of latent fingerprints on fluorescent substrates such as paper, cardboard, and fluorescent paint. Ordinary fluorescent imaging of latent fingerprints on these surfaces results in poor contrast. Instead, the specimens are treated with a phosphorescent dye that preferentially adheres to the fingerprint which allows time-resolved discrimination between the fingerprint phosphorescence and the background fluorescence. Time resolved images are obtained by synchronizing the digital sampling of the specimen luminescence with the on-off cycle of the chopped illumination beam. The merit of this technique is illustrated with high contrast images of fingerprints obtained from the fluorescent painted surface of a Coke can.

Surface-profile reconstruction using reflection differential phase-contrast microscopy

The use of optical differential phase-contrast microscopy to obtain the surface profile of samples is outlined. The range of accurate feature height determination was calculated as a function of steepness of the side of the feature. Heights of thin features (height <0.1 microm) were accurately determined experimentally. Sample tilting and oblique stage scanning were required in order to determine the heights of thicker samples. Reconstructed profile heights were measured as a function of defocus.

Fingerprint Imaging with a Confocal Scanning Laser Macroscope

The scanning laser macroscope is a new scanning beam confocal imaging system that scans up to 7.5 cm × 7.5 cm in 5 seconds. One of its unique features is a telecentric f-theta lens that focuses the incoming beam from a low power laser to a 10 µm spot on the sample. The f-theta lens provides a linear scan, and has a flat focal plane. The macroscope is described in detail and its operation is discussed. Confocal reflected-light images of latent fingerprints were obtained on several different materials. Fluorescence images of Rhodamine-treated samples were also obtained. We also show a reflection image of a fingerprint recorded by scanning the finger in air. Other possible uses of the macroscope in forensics include time-resolved fluorescence, imaging of fluorescent gels used in DNA fingerprinting, IR fluorescence imaging of documents, detecting and recording fluorescence images of latent fingerprints excited with UV radiation, and entering file prints into the computer for storage.

Confocal imaging of porous silicon with a scanning laser macroscope/microscope

Abstract High resolution, large area photoluminescence mapping with scanning stage microscopes has proven to be a useful, but slow, quality control technique for compound semiconductor wafers. This paper describes a confocal scanning beam MACROscope-Microscope which can image specimens up to 7.5×7.5 cm in size, in less than 10s, using reflected light, photoluminescence, and optical beam induced current. MACROscope mode provides 5 μm lateral resolution and 300 μm axial resolution. Microscope mode provides 0.25 μm lateral and 0.5 μm axial resolution, with a minimum field of view of 25×25 μm. This instrument can be used to evaluate preparation parameters involved in the manufacture of porous silicon as well as to provide quality control at a macroscopic and microscopic level for the fabrication of porous silicon specimens, wafers, detectors, and similar devices. A brief introduction to confocal microscopy and porous silicon is given. Several confocal and non-confocal photoluminescence and reflected-light images of a porous silicon wafer are shown at macroscopic and microscopic levels. A 3D profile of porous silicon structures reconstructed from confocal slices is also shown.

Single-pinhole confocal differential phase contrast microscopy

A new technique for obtaining confocal differential phase contrast is outlined. It is shown that this method involving a single pinhole and a split detector is easier to align and calibrate than the standard method of two pinholes and two detectors. Experimental calibration curves, which show that this arrangement does perform differential phase contrast imaging and that it can be used to measure surface height variations of the order of λ/600 per micrometer, are presented. Confocal scanning-beam reflection and transmission differential phase contrast images are presented.

Confocal scanning beam laser microscope/macroscope: applications in fluorescence

A new confocal scanning beam laser microscope/macroscope is described that combines the rapid scan of a scanning beam laser microscope with the large specimen capability of a scanning stage microscope. This instrument combines an infinity-corrected confocal scanning laser microscope with a scanning laser macroscope that uses a telecentric f*(Theta) laser scan lens to produce a confocal imaging system with a resolution of 0.25 microns at a field of view of 25 microns and 5 microns at a field of view of 75,000 microns. The frame rate is 5 seconds per frame for a 512 by 512 pixel image, and 25 seconds for a 2048 by 2048 pixel image. Applications in fluorescence are discussed that focus on two important advantages of the instrument over a confocal scanning laser microscope: an extremely wide range of magnification, and the ability to image very large specimens. Examples are presented of fluorescence and reflected-light images of high quality printing, fluorescence images of latent fingerprints, packaging foam, and confocal autofluorescence images of a cricket.