Harry A. Atwater - US grants

This research project is directed in two major thrust areas (i) processing of metal alloys and (ii) processing of semiconductor materials. A component connecting both of these areas is simulation and theory work aimed at predicting materials properties. The metal processing research employs ion beam mixing, shock consolidation, mechanical alloying, and synthesis of layered and metastable materials. The semiconductor processing research employs epitaxial growth on Si and GaAs, ion implantation, nucleation and growth on new phases such as amorphous carbon. The use of sophisticated electron microscopy apparatus is central to the research projects. Better understanding of the influence of interfaces, surfaces and grain boundaries on materials properties is a primary goal of this reserach.

A quantum cluster dot is a compact structure in the 5 to 20 um size range where small scale in three dimensions yields discrete electronic states. This research is an interdisplinary, experimental program for the formation and characterization of monodisperse gallium arsenide (G A ) quantum cluster dots. The clusters will be produced in an aerosol reactor by the vapor phase reaction of an organometallic gallium contains vapor with arsine. Particle size and cluster quality will be monitored by in-situ laser induced luminescence spectra. Clusters from the aerosol reactor will be classified into very narrow size ranges required for applications by an electrostatic classifier. Captured particles will be analyzed as to particle morphology, interval defect structure, and carbon contamination using electron microscopy (TEM and STEM), energy dispersive X-ray analysis (EDAX), and electron energy loss spectroscopy (EELS). Exciting new electronic and optical components would result from the incorporation of large numbers of identical quantum cluster dots into solid state structures. Possible applications include semiconductor lasers several orders of magnitude better than conventional diode lasers and new electroluminescent display technology with convenient adjustment of color. However, to achieve such results, the clusters must be produced to very strict size tolerances, typically with size variations not larger than 0.5 um. Otherwise a device averaging the electronic states of many clusters varying in size would lose the distinctness of states inherent in any individual quantum cluster dot.

Dr. Atwater has been selected as Presidential Young Investigator. He is active in fundamental research on the use of ion beam techniques to study semiconducting materials. In the research program for the National Science Foundation he will pursue studies to include the following: (1) study of the interaction of a ion beam collision cascade with interfaces, (2) study of motion of interfaces in semiconductor, metal, and alloy thin films as a function of ion beam cascade density, (3) measurement and computer simulation (using molecular dynamics techniques) of grain growth during cascade events, (4) study of stability and crystal/amorphous phase transformations as a function of critical ion flux and temperature for silicon, (5) study of critical conditions for homogeneous nucleation of the amorphous phase for silicon/vapor interfaces. The research in this grant will have an impact on electronics and opto-electronic technology. The interactions with industry which are inherent with Presidential Young investigator grants will have implications for national competitiveness in this critical technology.

New device simulation and layout tools and a new device fabrication process are being developed for the Caltech freshman course in solid state devices and integrated circuits, a two-quarter sequence offered annually to approximately 90 majors and non-majors. The unusual goal of this class is to excite interest among freshman in solid state electronics in particular, and engineering in general. Hence the underlying curricular strategy is to appropriately simplify device physics to the level of intuition and simple mathematics, and to simplify the fabrication process as much as possible so as to make the first undergraduate laboratory experience very positive. To this end, design of a software toolbox for device simulation and layout enables freshmen to better understand device operation at an intuitive level and to avoid design mistakes in device and circuit layout. A new fabrication process centered around the use of spin-dopants will allow use of both n-type and p-type dopants with greater ease, reliability and safety. Device simulation and layout tools and the use of both dopant types will enable the present curriculum to be expanded to the design and fabrication of bipolar and CMOS devices while retaining the simplicity crucial for the process. This will be a significant advance in the teaching of undergraduate courses in the design and fabrication of microelectronic devices.

A fundamental investigation of reflection electron energy loss spectroscopy in conjunction with epitaxial growth will be conducted. In situ measurement of core loss ionization and electron energy loss fine structure will be performed during thin film growth by molecular beam epitaxy. These measurements will enable investigation of surface dynamical phenomena during growth, such as surface segregation and relaxation of local order in films at the monolayer level. Of particular interest are the relation etween cation-anion flux ration, surface composition and surface reconstruction for group III-V semiconductor surfaces, and relaxation of local order at group IV(e.g., Si, Ge, Sn) alloy surfaces. Development of a data-parallel ultrahigh vacuum spectrometer will enable increases in data acquisition speed by approximatel;y 2-3 orders of magnitude. %%% This research will investigate a new method for compositional and stuctural analysis of thin films during the actual growth process. Potential benefits include the ability to achieve atomic level control over thin film composition, and semiconductor materials with novel properties and performance for use in advanced electronic and photonic devices and integrated circuits.

Harry Atwater Abstract The acquistion of a quantitative high-resolution video imaging system is proposed. The system will be used in conjunction with existing transmission electron microscopes for (i) atomic-scale imaging of thin films and nanoparticles, (ii) energy-filtered imaging of thin films and nanoparticles, (iii) quantitative electron diffraction nmeasurements,a nd (iv) facilitating the teaching of electron microscopy and microanalyis of materials. ***

9503210 Atwater This research aims at a definitive assessment of the synthesis, structure and electronic structure of a class of Group IV semiconductor alloys containing tin. New approaches to alloy synthesis will be explored to overcome thermodynamic and kinetic limits to growth of homogeneous, single-crystal, Sn-based group IV semiconductor alloys. Two types of epitaxial heterostructures are of interest: Binary alloys with large misfit relative to silicon grown either in thick strain-relieved layers or thin, coherently strained layers; and alloys where atomic size differences enable local strain compensation and low misfit relative to silicon. First principles electronic structure calculations in the local density approximation will be performed to enable determination of which structures are stable and to obtain energy band structures of strained and unstrained Sn-based alloys. Information from the electronic structure calculations will be used to construct force fields for molecular dynamics simulations of Sn incorporation using energetic beams. Measurements of electronic and optical properties (e.g. optical energy gap, carrier mobilities and carrier concentrations) of single crystal alloy films will be compared to calculated electronic and optical properties. %%% This program will be the first comprehensive investigation of a new class of materials whose electronic properties may result in the integration of new functional heterojunction electronic and optoelectronic materials and devices on silicon substrates. Because of the pervasiveness of silicon integrated circuit technology and its enormous economic importance, the technological impact of the proposed program is potentially very large. An important feature of the program is the training of students in a fundamentally and technologically significant area of materials research. ***

Goodwin 9529309 In the last five years, considerable effort has been devoted to diagnostic analysis of the plumes of matter produced when pulsed lasers are used to ablate a solid target. this has been primarily motivated by a desire to better understand the basic physical and chemical processes important to pulsed laser deposition, a newly popular thin film growth technique which is finding ever-increasing application to growth of superconductor, insulator and semiconductor structures. The objective from laser-induced plumes, rather than to study exclusively plume formation. The approach taken is a combined experimental and theoretical effort. Briefly, the aim is to determine the extent to which film stoichiometry and microstructure are determined by: Evolution of the energy distributions (both translational and internal) of the gas phase species as the plume approaches a substrate for thin film growth. The incident species' energy will affect the sticking probability, the dissociate probability and mode of dissociation and incorporation (i.e., adsorption or implantation) of gas phase constituents into the films. Evolution of species distributions as the plume moves from the target to the substrate, including formation of reactive intermediates in the gas phase, which then condense onto the solid surface. Prominent aspects of the experimental work are laser-induced fluorescence (LIF) measurements of gas phase plume an intermediate species in their electronic ground states, in situ surface analysis by reflection high energy electron diffraction (RHEED) and a complementary core level spectroscopy technique developed at Caltech, reflection electron energy loss spectroscopy (REELS). Various forms of postgrowth film microstructural analysis will be used to analyze film stoichiometry, density, crystallinity, bonding state, and optical properties. The theoretical work will involve several efforts, including molecular dynamics (MD) simulations of energetic plume-surface interact ions and Director-Simulation Monte Carlo (DSMC) simulations of gas-phase plume dynamics, including chemical kinetics and substrate interactions. ***

9871850 Atwater This objectives of this project are to develop the synthesis, processing, manipulation and characterization tools to enable and improve novel, emerging silicon nanoparticle memory and logic devices. These devices exploit common approaches for particle synthesis, manipulation, interface passivation and electrical and optical characterization of ordered, passivated arrays of size-classified silicon nanoparticles which are integrated into larger device structures. Device structures to be addressed in this project include: a nonvolatile memory based on discrete charge storage on the nanoparticle floating gate of a field-effect transistor, and a silicon nanoparticle-based implementation for a cellular automata wire/logic gate, in which information is propagated by cell-cell electrostatic interactions rather than by current flow. The nanoparticle engineering and assembly methods developed in this program may enable the first realization of a cellular automata logic gate capable of room temperature operation. Key aspects of the synthesis and processing are engineering of nanoparticle size, shape, dielectric passivation thickness and stoichiometry, and control of nanoparticle position. Control of position is achieved in model device structures using force manipulation by a scanning probe microscope. Another effort is aimed at utilizing fluid and colloidal forces to fabricate ordered linear and planar arrays. Characterization of charge state and morphology at the single particle level is performed using conducting tip atomic force microscopy. %%% The project addresses basic research issues in a topical area of science and engineering having high technological relevance. The research will contribute new knowledge at a fundamental level to important aspects of electronic devices. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance of advanced devices by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. This research grant is made under the Nanotechnology Initiative (NSF 98-20), and is co-funded by the Directorate for Engineering, the Directorate for Computer and Information Science and Engineering, and the Directorate for Mathematical and Physical Sciences. The research team is a university/industry/government lab collaboration between Applied Physics and Chemical Engineering faculty at the California Institute of Technology, and technical staff at Bell Labs/Lucent Technologies and the Jet Propulsion Laboratory.

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Atwater

This grant will help develop quantitative electrostatic force scanning probe
microscopy. The project includes modification of a commercial ultrahigh
vacuum scanning probe microscope and development of new electrostatic force
microscopy simulation software. The program comprised both ultrahigh
vacuum electrostatic force microscopy measurements and development and
testing of finite element electrostatic simulation software describing
tip-sample interactions, including van der Waals and electrostatic force
contributions . This will enable more quantitative understanding of
nanometer-scale charge distributions and low mobility electronic
transport. The immediate scientific use for the instrument will be in a
collaborative Caltech/Bell Labs/NASA-JPL multi-investigator research
program aimed at probing charge injection and storage in silicon
nanoparticle structures for nonvolatile memory applications. Information
and software needed to perform quantitative EFM will be disseminated to the
materials research community.

Electrically insulating thin films are critical and ubiquitous components
of electronic devices such as integrated circuits and micromechanical
devices. Trapping of electronic charge, whether by design or as an
unintended effect, is a common characteristic of insulating thin films. It
is desirable to be able to quantitatively measure the extent of and
mechanisms for charge trapping in order to better understand the
performance and reliability of insulating thin films. Scanning probe
microscope techniques such as electrostatic force microscopy have opened a
new vista in the understanding charge trapping in insulators because they
enable measurement at nanometer-scale spatial resolution and total charge
sensitivity down to the single electron level. To date, such electrostatic
force microscopy measurements have been used as a qualitative but not a
quantitative tool for understanding charge trapping in insulators. This
project aims to put the electrostatic force microscopy method on a firm
quantitative foundation, through a combination of measurements and
development of simulation software needed for quantitative
understanding. The results will be applied to characterize charge trapping
in nonvolatile floating gate memory device materials containing
semiconductor nanocrystals. These materials and the devices made with them
are very promising candidates for the next-generation of ultradense,
low-power nonvolatile "flash" memory chips like those now used widely in
portable electronic devices such as wireless telephones, pagers, electronic
cameras and personal digital assistants.

The Materials Research Science and Engineering Center (MRSEC) at the California Institute of Technology supports an interdisciplinary research program on advanced materials, as well as a wide range of educational activities, including outreach to minority communities in California both at the pre-college and college level, and development of pre-college instructional materials. The Center supports well maintained shared experimental facilities and also supports interactive efforts with industry and other sectors.

The Center's research is organized into two interdisciplinary research groups (IRG). IRG 1, Biological Synthesis and Assembly of Macromolecular Materials, uses powerful biological approaches for the synthesis and assembly of polymeric materials. IRG 2, Bulk Metallic Glasses and Composites, explores new strategies to produce bulk metallic glasses and their composites with enhanced mechanical properties. The Center also provides seed support for emerging research opportunities in photonic and ferroelectric materials.

Participants in the Center currently include 18 senior investigators, 1 postdoctoral associate, 17 graduate students, 16 undergraduates, and 8 technicians and other support personnel. Professor Julia A. Kornfield directs the MRSEC.

This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119). We propose a joint Caltech/NASA-JPL/Agere Systems research program to develop new materials for Si nanocrystal nonvolatile memories and related nanoscale electronic devices. Under the program:

o New aerosol-based Si nanoparticle and nanowire engineering methods will be developed to enable formation nanoparticle and nanowire arrays with precise control of particle size, particle number and array structure. These methods 'will be compatible with Si ultralarge scale integrated (ULSI) circuit process technology.
o Aerosol-synthesized and colloidally processed silicon nanoparticle and nanowire arrays with novel configurations will be integrated into Si-based metal-oxide-semiconductor (MOS) devices at state-of-the-art device dimensions yielding nanometer-scale memory devices.
o A dielectric heterostructure layered tunnel barrier will be developed to achieve simultaneous ultrafast chargc injection and extremely long charge retention times, which are mutually exclusive for existing conventional dielectric tunnel baffler designs.
o Nanocrystal charging via electrical injection and photoexcited carrier injection will be studied to assess layered tunnel barrier performance and to determine whether quantum size effects on the density of electronic states can be exploited for control of electronic charging energy.

The focal point of the work is a recently demonstrated high-performance aerosol silicon nanocrystal memory device, developed by the present nanoscale interdisciplinary research (NIRT) team under prior NSF support. Silicon nanoparticles comprise the floating gate that is the storage node of a nanocrystal nonvolatile memory. Aerosol synthesis allows control of Si nanocrystal size and shape that are difficult to achieve by other synthesis methods. Uniquely, our team has successfully integrated vapor-synthesized aerosol nanoparticles into a high-performance silicon-based electronic device, fabricated at 0.18 micron design rules on 200 mm substrates by ultraclean processing at state-of-the-au device dimensions. Extensive electrical characterization of transistor subthreshold and turn-on performance, retention time, program-erase cycling, gate and drain disturb characteristics indicated that these devices are high performance memory devices. The Caltech/JPL/Agere NIRT team is unusual in its combination of basic research on new electronic materials developed at Caltech followed by direct materials integration into a flexible, state-of-the-au silicon device process carried out at Caltech and Agere System's fabrication facilities.

A conference on Cat-CVD (Hot-Wire CVD) Processing, http://www.nrel.gov/cat-cvd2/ , will be held in Denver, CO September 10-13, 2002. The conference objective is to provide a forum for discussion to assess and understand the deposition of Si and other thin film related materials by the Cat-CVD (Hot-Wire CVD) process, to address deposition related processing issues, and investigate new applications which may lead to industrial utilization of this rapidly maturing technology.
The program is organized as a workshop-style conference to provide an interdisciplinary forum for device engineers, solid state physicists, and materials scientists to discuss topics of common interest both formally through invited and contributed presentations, and informally during a variety of events including a poster presentation session. Objectives are to stimulate communications among the community of researchers addressing Hot-Wire CVD Processing and its relationship to technology. A variety of disciplinary backgrounds-chemistry, physics, engineering and materials science, is represented and contrributes positively to the intellectual content of the Conference. Along with the opportunity to assess the field and future directions, it is expected that new ties will be established between universities, government research institutions, and industry.
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An evaluation of the progress and status of Hot-Wire CVD Processing and related device issues along with current assessments of the most important developments will be of significant value to the understanding and enhanced utilization of electronic materials in computing, data processing, and communications. To promote and sustain the growth of such technologies, it is vital to attract the support, enthusiasm, and interest of young researchers and students. To this end, sessions will be held sequentially, and special efforts made to ensure information exchange in an informal setting. Leading scientists in the Si field have committed to attend the conference, so there will be opportunity for interactions between researchers of all levels of experience in Cat-CVD.
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Scherer
This proposed instrumentation acquisition is that of a dual-beam focused ion beam scanning electron microscope (FIB/SEM) system, with which the involved research team intends to investigate electromagnetic phenomena at the nanometer scale. The involved research 'team' includes three collaborative elements. CalTech will take the lead, JPL will provide supplemental input, and the FIB/SEM vendor (i.e., FEI Inc.) will not only furnish the basic hardware but will interactively assist CalTech students and faculty in their efforts with software optimization.

Under renewed NSF support, The Center for the Science and Engineering of Materials (CSEM) at Caltech will carry forward its mission as a multifaceted materials research and education center. CSEM combines world-class materials research programs organized as interdisciplinary research groups and seed research projects, with educational programs serving underrepresented minority undergraduate, community college, and high school students across Southern California and also serving the general public via television-based mass media programming.

The Center will address both research and educational aspects of materials science in several areas: i) Macromolecular materials design to produce tailored responses to cellular adhesion and growth; ii) novel ferroelectric photonic materials that enable new freedoms in tuning the dispersion relations for photonic materials and devices and offer a new avenue for scientific progress in using light to understand complex materials behavior; and iii) advanced structural materials based on bulk metallic glass composites, with the potential to enable new amorphous structural materials with strength-to-weight ratio much higher than steel.

CSEM also supports emerging research areas via seed projects, which will focus on i) catalytic materials for chemical storage of hydrogen via methanol production and use in nonpolymer fuel cells based on "superprotonic" solid acids and ii) spintronic and optoelectronic properties of organic semiconductor/ferromagnetic heterostructures with applications in future electronic and quantum computing devices.

Technical: This research project addresses active plasmonic materials and prototype devices. Plasmonics has focused largely on passive metallodielectric structures to control wave dispersion and propagation in planar waveguides, subwavelength scale apertures and nanoparticle arrays. While passive plasmonic materials enable plasmonic components interconnected in circuit-like networks, greater functionality will be possible in plasmonic components and networks if active plasmonic materials/devices can be realized. The approach centers on synthesis and characterization of new plasmonic materials which may enable plasmon emission, nonlinearity and gain for potential plasmonic device applications. The goal is to form the materials foundation for enabling compact plasmonic sources and nonlinear plasmonic and nanophotonic components useful for integration into nanophotonic circuits containing linear and nonlinear elements for applications such as chip-based optical switching, imaging, and molecular spectroscopy. The concepts and materials research addresses three specific application areas. The first is materials research for realization of ultracompact subwavelength photonic switches based on electro-optical and nonlinear optical modulation of plasmonic hole-array and nanoparticle array transmission. The second area is realization of surface plasmon emission sources, including light-emitting structures featuring plasmon-enhanced light emission and spectrally-tuned spontaneous emission as well as purely bound plasmon-generating material configurations. The third area is the design and confinement of plasmonic modes within subwavelength mode volumes in annular Bragg resonator surface plasmon cavities. Investigation of these structures is expected to yield new insights about the nature of surface electromagnetic wave propagation and scattering at metal interfaces and the radiative emission properties of quantum dots and dipole emitters strongly perturbed by local fields near metallic nanostructures. The approach includes theoretical and experimental activities. Theoretical work will focus on analytic modeling as well as full-field electromagnetic simulations using finite difference time domain and beam propagation methods that guide the design of plasmonic structures. Experimental work will focus on developing active plasmonic structure fabrication, including lithographic fabrication of plasmonic cavities, integration of active semiconductor nanocrystal media (Si, CdSe and the IV-VI lead salts PbS and PbSe).
Non-Technical: The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities for potential next generation electronic/photonic devices. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project includes i) training of graduate researchers in the emerging areas of plasmonics and nanophotonics ii) educational outreach to minority undergraduate students via summer undergraduate research at Caltech and iii) research dissemination in the worldwide plasmonics community via a newly-founded Gordon Research Conference on plasmonics, to be held for the first time in summer 2006. Graduate research training involves materials science and applied physics of surface plasmon emission sources and nonlinear phenomena in plasmonic materials. Minority undergraduate students will be identified through Caltech's Minority Undergraduate Fellowship program, GradPreview program and via interactions with the Materials Partnership between Caltech and California State University Los Angeles. The principal investigator will serve as Vice-Chair of the new Plasmonics Gordon Conference, whose goal is to advance the plasmonics field through stimulating interdisciplinary presentation and discussion at the frontiers of science.

This Major Research Instrumentation (MRI) grant will enable the acquisition of a three-ion-beam microscope, the ORION NanoFab system, from Carl Zeiss Microscopy. This tri-beam system can provide unprecedented resolution, precision and versatility for the fabrication and characterization of materials and devices all the way down to the nanometer scale (roughly a few times the atomic spacing). The ORION NanoFab system is expected to make a significant impact on interdisciplinary nanoscience research, particularly in the areas of quantum matter and technology, medical and bio-engineering, photonic and optoelectronic research, meta-materials, and renewable energy science. The tri-beam system will be located at the Kavli Nanoscience Institute (KNI) of the California Institute of Technology (Caltech), which provides laboratories with state-of-the-art infrastructure and houses centralized nanofabrication and nano-characterization facilities for researchers at Caltech, the Jet Propulsion Laboratory (JPL), and corporations and other institutes in the greater area of Southern California. As this form of tri-beam microscopy is only in its infancy, Caltech will also be partnering with Zeiss in a technical outreach effort to bring experts together to advance new ideas and applications of the tri-beam tool. This collaborative outreach plan includes: hosting annual workshops at Caltech with industrial and global research-community users of the ORION NanoFab to exchange information on research highlights, technical challenges, and new technical developments and applications. As part of outreach effort there is also a plan to offer nanoscience "demo days" for K-12 students in which the advanced instrumentation of the ORION NanoFab and other tools in the KNI can be used to explore the nanoscopic world, as well as lectures and lab tours at Caltech to local high school students and teachers on topics of nano-science and technology (nano-S&T) and applications of modern microscopy.

This Major Research Instrumentation (MRI) grant will enable the acquisition of a three-ion-beam microscope, the ORION NanoFab system, from Carl Zeiss Microscopy. The ORION NanoFab is a three-ion-beam nano fabrication and microscopy system capable of an imaging resolution of 0.5 nm and a cutting resolution of ≲2nm, virtually independent of material. The system is designed to seamlessly switch between gallium, neon and helium beams, so that one has the option of employing the gallium focused ion beam (FIB) to pattern materials at the micro-scale, taking advantage of the powerful yet gentle neon beam for precision nano-machining with speed, or using the helium beam to fabricate delicate sub-10 nm structures that demand extremely high machining fidelity and/or cutting of delicate materials (such as graphene) that are prone to damage by high-energy electrons or heavy-element ion beams. Its capability of maskless nano-patterning also minimizes possible contamination due to the multiple steps required in processing and removing masks. The ORION NanoFab system is expected to make a significant impact on interdisciplinary nanoscience research, particularly in the areas of quantum matter and technology, medical and bio-engineering, photonic and optoelectronic research, meta-materials, and renewable energy science. The tri-beam system will be located at the Kavli Nanoscience Institute (KNI) of the California Institute of Technology (Caltech), which provides laboratories with state-of-the-art infrastructure and houses centralized nanofabrication and nano-characterization facilities for researchers at Caltech, the Jet Propulsion Laboratory (JPL), and corporations and other institutes in the greater area of Southern California. In partnership with Zeiss we also plan to bring together the industrial and global research-communities in a series of annual workshops at Caltech designed to help advance the technology and applications of multi-beam microscopy and nanofabrication.

The broader impact of this I-Corps project is to increase the efficiency of solar modules by up to 6%, a significant improvement in the photovoltaics (PV) space. This project replacies standard screen-printed metal contacts with an effectively transparent contacts (ETC) where the shading loss is brought down to 0%. A significant fraction of the PV ecosystem will benefit from this technology. ETCs can enable solar module manufacturers to fabricate up to 6% higher relative efficiency solar modules. This higher efficiency can lead to reduced cost overall for land use, transportation, installation and cleaning. Therefore, the levelized cost of electricity (LCOE) can potentially be reduced and photovoltaic electricity can become more affordable.

This I-Corps project further develops effectively transparent contacts (ETC) that mitigate shading losses inherent to screen-printed metal contacts over the entire solar spectrum and for all angles of incidence. ETCs are triangular cross-section micro-scale metal contacts that redirect the incoming light efficiently to the active area of the solar cell. Overcoming front contact shading loss without reducing the grid conductivity increases the silicon solar cell power output by up to 6%. When replacing standard screen-printed metal contacts with ETCs the amount of used silver can also be reduced. The ETC's are made via a residue-free three-dimensional micro-imprint process that enables large scale printing of ETCs by solar module manufactures. To date, the integration of ETCs with state-of-the-art silicon heterojunction solar cells has been successfully demonstrated on a laboratory scale.