Daniel Moses

Low energy ion implantation and electrochemical separation of diamond films

We combine low energy and low dose ion implantation with an electrochemical etch to fabricate thin diamond layers suitable for seeding homoepitaxial or polycrystalline chemical vapor deposited (CVD) diamond growth. Implantation of a carbon ion dose of 1×1016 cm−2 at 175 keV creates subsurface damage in a bulk crystal which is selectively removed by the electrochemical etch. Implanted substrates were subjected to CVD diamond deposition prior to etching of the damage layer. We discuss the effect of implantation and subsequent annealing conditions on the morphology and Raman spectra of the CVD films. All results indicate that the seed layer nucleated high quality CVD diamond film growth.

Diamond metal-semiconductor-metal ultraviolet photodetectors

Abstract Metal-semiconductor-metal photodetectors have been fabricated in natural, synthetic, and polycrystalline insulating diamonds. The detectors were characterized over a wavelength range of 130–700 nm. Low dark currents of 10–12 A were observed. Of the materials investigated, natural diamond demonstrated the highest quantum efficiency of 39% at a wavelength of 200 nm and a factor of 103 lower response to visible light.

Electrochemical Patterning of Amorphous Carbon on Diamond

The ability to pattern ion-implantation damaged or other nondiamond carbon on a diamond substrate is useful for fabricating a variety of devices. We accomplished such patterning by an unmasked implantation into a diamond substrate followed by photolithography and a selective electrochemical etch. The use of a high resistivity medium coupled with applied biases over 50 V permitted etching without requiring contact between the substrate and an electrode. Many electrolytes gave etches that exhibit high selectivity for nondiamond carbon over both diamond and dielectrics such as photoresist. Optical, electrical, and Raman spectroscopic measurements elucidate the effects of the etch on the implanted diamond surface.

Optical characterization of diamond MIS capacitors

The transient photoresponse properties of diamond metal-insulator-semiconductor (MIS) capacitors have been characterized for the first time. Capacitors were fabricated on natural diamond using an electrochemical cleaning step with a CVD SiO/sub 2/ dielectric and an optional carbon implantation to create a nonuniform doping profile. Devices were found to function as integrating photodetectors and were evaluated by the spectral dependence of the transient photocapacitance (PC). We discuss a model that distinguishes between the responses due to inversion layer population and that due to bulk trap occupancy changes. Inversion charge generation was observed at all wavelengths investigated and it dominated the PC transient at photon energies above 3 eV. Possible reasons for this result are discussed and analyzed. We could not demonstrate a suitable way to use carbon implantation to form a surface n-type layer in a MIS device without degrading the device IV properties and eliminating the integrating photoresponse observed on non-implanted devices. These results suggest that diamond charge-storage devices can function only if the diamond surface is prepared properly before device fabrication. >

METIS, the Multi Element Telescope for Imaging and Spectroscopy: An instrument proposed for the solar orbiter mission

METIS, the Multi Element Telescope for Imaging and Spectroscopy, is an instrument proposed to the European Space Agency to be part of the payload of the Solar Orbiter mission. The instrument design has been conceived for performing extreme ultraviolet (EUV) spectroscopy both on the solar disk and off-limb, and near-Sun coronagraphy and spectroscopy. The proposed instrument suite consists of three different interconnected elements, COR, EUS and SOCS, sharing the same optical bench, electronics, and S/C heat shield aperture. COR is a visible-EUV multiband coronagraph based on a classical externally occulted design. EUS is the component of the METIS EUV disk spectrometer which includes the telescope and all the related mechanisms. Finally, SOCS is the METIS spectroscopic component including the dispersive system and the detectors. The capability of inserting a small telescope collecting coronal light has been added to perform also EUV coronal spectroscopy. METIS can simultaneously image the visible and ultraviolet emission of the solar corona and diagnose, with unprecedented temporal coverage and space resolution the structure and dynamics of the full corona in the range from 1.2 to 3.0 (1.6 to 4.1) solar radii (R⊙, measured from Sun centre) at minimum (maximum) perihelion during the nominal mission. It can also perform spectroscopic observations of the solar disk and out to 1.4 R⊙ within the 50-150 nm spectral region, and of the geo-effective coronal region 1.7-2.7 R⊙ within the 30-125 nm spectral band.

Evaluation of the stray light from the diffraction of METIS coronagraph external occulter

METIS (Multi Element Telescope for Imaging and Spectroscopy) is an externally occulted coronagraph part of the Solar Orbiter payload. METIS innovative occulting system, called inverted externally occulter (IEO), consists of a circular aperture, IEO, that acts also as the entrance pupil of the instrument, and a solar disk rejection mirror (M0), placed at the bottom end of the coronagraph boom. M0 reflects back through IEO the solar disk radiation, letting the coronal radiation enter the coronagraph telescope. Light diffracted by IEO enters the telescope and has to be minimized with a proper shape of the IEO edge. The paper describes the theoretical results of the diffraction analysis extended to the scattered light by the primary mirror of the telescope onto the primary focal plane. A summary of the entire stray light reduction capabilities of METIS is also given.

SOLARIS: Solar sail investigation of the Sun

In this paper, we detail the scientific objectives and outline a strawman payload of the SOLAR sail Investigation of the Sun (SOLARIS). The science objectives are to study the 3D structure of the solar magnetic and velocity field, the variation of total solar irradiance with latitude, and the structure of the corona. We show how we can meet these science objective using solar-sail technologies currently under development. We provide a tentative mission profile considering several trade-off approaches. We also provide a tentative mass budget breakdown and a perspective for a programmatic implementation.

Optical design of a high-spatial-resolution extreme-ultraviolet spectroheliograph for the transition region

A spectroheliograph dedicated to the observation of the solar disk in the extreme-ultraviolet OV spectral line at 62.97 nm is described. As demonstrated in the Skylab SO-82A spectroheliograph [Appl. Opt. 16, 870 (1977)], this line is uniquely suited to characterize solar plasma in the important 250, 000 K temperature regime. No multilayer coating or suitable filter is yet available to select this wavelength, so an optical design based on a double spectrograph with a spatial filter to remove the unwanted radiation has been developed. Analysis of the optical design shows that this instrument can obtain a 1 arcsec spatial resolution (two pixels) with a relatively high image-acquisition cadence. A preliminary tolerance analysis has been performed. A simple method of instrument alignment in visible light is also described.

SPECTRE: a spectro-heliograph for the transition region

The SPECtro-heliograph for the Transition REgion (SPECTRE) experiment is one of the instruments of the Solar Heliospheric Activity Research and Prediction Program (SHARPP) suite initially foreseen aboard the NASA mission Solar Dynamics Observatory (SDO) of the International Living With a Star (ILWS) program. The scientific objective of the SPECTRE experiment was to characterize the rapid evolution of plasma in the transition region of the solar atmosphere, producing full-disk 1.2 arcsec-resolution images of the solar atmosphere at the very critical 63 nm OV spectral line, characterizing a solar plasma temperature of about 250,000 K. Unfortunately, NASA very recently and unexpectedly, during the instrument Phase A study, decided not to proceed with the realization of SHARPP. The authors of this paper think that all the work done so far in the definition of SPECTRE should not be lost. So, they have decided to summarize in this paper the main characteristics of this instrument and the results of the analysis so far performed: the hope is that in a next future this work can be used again for realizing an instrument having similar characteristics.

Evaluation of Tektronix 1024 MPP frontside and backside CCDs for the SOHO program

A program to build 1024 x 1024 21 micron MPP-CCDs for the NASA/ESA Solar and Heliospheric Observatory (SOHO) spacecraft is in progress. A test and evaluation facility has been constructed to evaluate and select the CCDs for flight. Parametric studies of voltage rails timing pattern and horizontal and parallel clock timing are performed. Various CCD performance parameters are plotted including CTE photon transfer curve dark current output node gain and noise. We have found that the MPP CCD requires a different sequence of parallel phase timing when running in the fully inverted mode from the pattern required for the non-inverted mode or the non-MPP device. Also the backside MPP-CCD is extremely sensitive to the length of time for the parallel transfer. 1.