Actoprobe team had developed custom Tip Enhancement Raman Spectroscopy System (TERS) with specially developed Ultra High Aspect Ratio probes for AFM and TERS measurements for small pixel infrared FPA sidewall characterization. Using this system, we report on stimulated Raman scattering observed in a standard tip-enhanced Raman spectroscopy (TERS) experiment on GaSb materials excited by 637-nm pump laser light. We explain our results by TERS-inherent mechanisms of enormous local field enhancement and by the special design and geometry of the ultrahigh-aspect-ratio tips that enabled conditions for stimulated Raman scattering in the sample with greatly enhanced resonance Raman gain when aided by a microcavity to provide feedback mechanism for the Raman emission. The approach has great potential for further, orders-of-magnitude, progress in TERS enhancement by significantly increasing its nonlinear component. We report development of novel class of probes for atomic force microscopy (AFM active optical probe - AAOP) by integrating a laser source and a photodetector monolithically into the AFM probe. The AAOPs are designed to be used in a conventional AFM and would enhance its functionality to include that of the instruments (NSOM, TERS, hybrid AFM).
Growth of ZnTe and HgCdSe on Si has been pursued using molecular beam epitaxy (MBE) as a new
class of IR materials. Besides, ZnTe/Si can also be used as a lattice-matching, large area and low cost
alternate substrate for other III-V and II-VI compound semiconductors, such as GaSb based type-II
superlattice materials around 6.1A. We report in this paper our systematic studies on MBE growth conditions
for ZnTe(211) on Si and highlights of MBE growth of HgCdSe on ZnTe/Si. A close to optimal growth
window has been established for MBE growth of ZnTe(211)/Si(211) to achieve high crystalline quality, low
defect and dislocation densities as well as excellent surface morphology. Using this baseline MBE growth
process, we are able to obtain ZnTe(211)/Si wafers with X-ray full-width at half-maximum (FWHM) as low
as 70 arcsec, low dislocation density (~105 cm-2) and defect density (1000 cm-2).
Boron implantation and heterojunction epitaxy have been the standard techniques for the production of HgCdTe focal plane arrays for a variety of applications. Each of these techniques has its special advantageous features. In this paper, we will describe an advanced HgCdTe junction formation technique, the planar ion-implantation-isolated heterojunction process, which utilizes the benefits of both the boron implantation and the heterojunction epitaxy
techniques. HgCdTe arrays in the format of 320x256 and 640x512 have been produced by this method. The characteristics of these arrays are reported.
Factors that affect width and aspect ratio in electron cyclotron resonance (ECR) etched HgCdTe trenches are investigated. The ECR etch bias and anisotropy are determined by photoresist feature erosion rate. The physical characteristics of the trenches are attributed to ECR plasma etch chemistry.
Incorporating fullerene into DNQ novolak resist provides a 60 percent reduction in the ECR plasma etch rate in a hydrogen/argon plasma. The reduction in plasma etch rate was also accompanied by a 5 degree(s)C increase in the pattern flow temperature. Plasma etch resistance was added to the photoresist after pattern exposure. Fullerene incorporation was accomplished by pattern development in a C60 /tetra-methyl ammonium hydroxide (TMAH) solution.
To achieve the DoD objective of low cost high performance infrared focal plane arrays a manufacturing technique is required which is intrinsically flexible with respect to device configuration and cutoff wavelength and easily scaleable with respect to volume requirements. The approach adopted is to fully develop the technology of molecular beam epitaxy (MBE) to a level where detector array wafers with a variety of configurations can be fabricated with first pass success at a reduced cost. As a vapor phase process, MBE lends itself directly to: (1) the inclusion of real-time monitoring and process control, (2) a single or multiple wafer growth mode, (3) nearly instantaneous changes in growth parameters. A team has been assembled to carry out the program. It is composed of four industrial organizations -- Rockwell International, Hughes Aircraft Company, Texas Instruments, and Lockheed-Martin, and a university -- Georgia Tech Research Institute. Since team members are committed suppliers and users of IRFPAs, technology transfer among team members is accomplished in real-time. The technical approach has been focused on optimizing the processes necessary to fabricate p-on-n HgCdTe double layer heterostructure focal plane arrays, reducing process variance, and on documenting flexibility with respect to cutoff wavelength. Two device structures have been investigated and fabricated -- a 480 by 4 and a 128 by 128.
The crystallographic orientation of Cd1-xZnxTe (x approximately equals 0.045) grown by molecular beam epitaxy (MBE) on a clean (planar) (100) GaAs surface can be controlled by the proper choice of the GaAs surface stoichiometry. An As-stabilized surface initiates (100) oriented growth, while the Ga-stabilized surface yields (111) oriented growth. Cd1-xZnxTe (x approximately equals 0.045) MBE layers grown in recesses of shadow masked patterned (100) GaAs substrates were found to be in the (100) orientation regardless of whether precursor surfaces were stabilized with Ga or As. The epitaxial layer's orientation and optical properties were determined by backscattered electron channeling and low temperature photoluminescence measurements, respectively. CdZnTe layers grown in recesses showed improved optical features as compared to the layers grown on planar substrates.