Application Cover Page for MMPP Seed Grant This cover sheet and all proposal materials should be submitted as a single pdf file by COB Jan. 31, 2013 to: Ms. Cherilyn Davis:[email protected]

************************************** Project Director Name/ Academic Rank/Department/ e-mail: Roy Clarke/ Professor/Physics/ [email protected] Co-Principal Investigator Names/Departments/e-mails: N/A Other faculty involved (and Department): N/A Number of students involved (specify as undergraduate or graduate): 1 GSRA and 1 undergrad Is project part of a UROP, REU or PhD project?: PhD project for GSRA; REU for undergrad Title of Project: “Semiconductor Neutron Detector” Statement of relevance to MMPP: Seed funding proposal for developing a portable energy-resolving neutron detector for homeland security applications and nuclear personnel dosimetry. Amount of funding requested in this proposal; attach itemized budget (not counted in page limit): $24,680 (itemized budget attached) Facilities/ space available: Cf neutron source with moderator; low-noise charge amps; PI’s lab space and electronics test facilities (~1000 sf.) Agency/agencies to which future proposal would likely be submitted: DHS; DTRA; DOE; National Nuclear Security Administration (NNSA) Timeline of Work/ External proposal submission deadline: 3/1/15 Department Chair (or designate) Signature: Abstract of Proposed Research: 300 words or less attach as separate page (not counted in page limit): attached ********************** 1

Abstract

This is a request to seed a proposal to various agencies that have expressed an interest in our project to develop an innovative, compact solid-state neutron detector for non-proliferation and homeland security applications. This potentially game-changing detector, based on wide band gap Boron Nitride (BN), is constructed as a reverse-biased p-i-n planar diode structure fully integrated on an ASIC silicon platform. The current ongoing crisis in the shortage of 3He gas, traditionally used to construct neutron detectors for many applications, together with the need for more compact, portable designs, provides a strong motivation for accelerated research on solid state neutron detectors. [1] Our approach has many advantages: excellent gamma: neutron discrimination, directionality, and superior quantum efficiency enabled by solid-state density. Preliminary modeling predicts a quantum efficiency exceeding 50% for a 3 micron film of the densest cubic form, cBN. The key aspect here is the relatively high carrier mobility of cBN, >400 cm2/Vs, coupled with the wide band gap such that noise-free room temperature operation is made feasible. Another significant advantage is the compact geometry of the p-i-n diode design which can readily be integrated as a wearable sensor, providing real-time information on the presence and provenance of Special Nuclear Materials (SNM). [2] Target agencies for the proposal include the National Nuclear Safety Administration (NNSA), who have invited us to submit a proposal for a new detector development program due to be implemented within the next 12 months. Other applications opened up by the compact solid state design include portal array detectors and down-hole neutron characterization of hydrocarbons for oil and gas exploration. The specific goal of the seed project will be to test the BN p-i-n prototype, which has been constructed in the Lurie Nanofabrication Facility (LNF), and assess its capability for spectroscopic analysis of fast neutron detection. The PI will work with a graduate student and an undergrad REU student on these tasks during the 12 month work performance period, and the results will be used to support the preparation of a federal grant application.

2

A miniaturized, wearable, solid-state neutron detector Lead Organization: University of Michigan; SSC, San Diego Detector Description The prototype device isCollaboration: a p-i-n structure containing three regions: a BN Topic ERT-01: Detection Materials: Room p-doped Temperature Semiconductor Radiation Detectors region, an intrinsic BN layer and an n-doped region (Si substrate).and [3] When Relevance Goalsa neutron is captured by a 10 electrode B atom, which has one of the largest neutron crossOperation Targets/Performance p-type BN sections, it transmutes to reporting Li givingofoff an energetic • Real time detection and neutrons 10 7 intrinsic BN particle (~ 1.5MeV), the personnel BN(n,α) Li nuclear • Wearable sensor for by security reaction. In turn this energetic • Field-deployable remote sensingalpha particle generates n-type Silicon Low-noise n many electron-holeImpact pairs in the semiconductor regions Transformational and Uniqueness charge amp. • Enables personal real-time warning sensor and the charge pulse is collected bynuclear the electrodes and Approach FI Technical Fig. 1: Schematic of prototype semi• Provides critical missing element in amplified inaan ultra-low-noise charge amplifier. We are Approach detection: sensor on every person in the field ecElectronics conductor BN neutron detector. using the latest cooled-FET charge amplifiers for this • planar p-i-n diode architecture Advantages over state-of-art solutions • Miniaturized solid state technology: wearable •purpose. constructed on silicon platform • No pressurized gases, aircraft compatible •Transformational ASIC design for charge pulse amplifier Capabilities: The prototype solid-state detector, patented by the PI, [4] can • Fully Silicon ASIC integrated, inexpensive •form Compact  “Badge”  electronics  packaging the basis for fixed, mobile, and wearable neutron radiation monitoring. Small detectors will • Enables directional arrays, wireless connectivity Current Statusfirst, but larger detectors or detector arrays could also replace large volume 3He be developed •detectors. DHS funded feasibility studydevice completed Cost Schedule, Milestones Team The BN-based offers improvements in sensitivity, size, and weight, directionality, • PoC in place on materials and fab Year 1 -device design and modeling ($120k) power consumption, operator safety, transportability, and cost that will make detection of SNM • Characterization labs up and running Year 2 – device fab, testing, optimization ($150k) much easier and less expensive to implement. Personal radiation monitoring devices, covert Year 3 – array integration, add directionality (100k) Technical challenges and risks radiation monitoring, border inspections, and detection of illicit SNM trafficking are all areas • sensitivity comparable to He3 detectors can benefit the proposed •that integration of newfrom semiconductor with technology. Si Prime Organization: Univ. of Michigan, Ann Arbor Principal Invesigator: Prof. Roy Clarke •Expected ohmic contacts to BN Performance: The BN neutron detector specifically addresses many of the RTA-01 Manager: Alan Janos (good progress in allgoals. areas)As a solid, BNProgram neutron detection has a much higher density of atoms with high thermal

neutron absorption cross section (particularly if using isotopically enriched 10B, which is readily available) than gases such as 3He or BF3. For a given sensitivity, then, a BN solid-state detector will be much smaller in size (and weight) than a 3He gas proportional counter. For example, a cubic phase 10BN-based detector with an 11 cm 11 cm 10BN  area  and  a  50  μm  10BN thickness would have approximately the same sensitivity (101 cps/nv) as a 2 atm, 41.4-in. (105 cm) long 3 He tube detector with a 1 in. (2.5 cm) diameter and 39.4 in. (100 cm) active length (SaintGobain Crystals 100He3/152/25). And if six 8 cm 8 cm c10BN detector squares were arranged in a cube configuration, the resulting detector would have the same sensitivity as this much larger 3 He tube, and would also be capable of determining the direction of the incoming neutron flux.

n:γ  Ratio  of  Generated  Free  Carriers

1000000

100000

10000 3

He (2 atm)

1000 Approximate minimum γ    energy from natural sources

10

BN

100 Material thicknesses adjusted to give thermal neutron absorption of 80%.

10 0.001

0.01

0.1

γ  Energy  (MeV)

3

1

10

100

Figure 2. Calculated ratio of free charge generated by thermal neutron interaction with listed materials relative to that generated by gamma ray interaction.

Furthermore, BN consists of relatively light elements and so has a very low (energy dependent) absorption  coefficient  for  γ-rays.  Discrimination  against  γ-rays, relative to neutrons, is therefore extremely high. For a 10BN neutron detector that absorbs 80% of incident neutrons, the calculated amount of free charge created by reaction with a thermal neutron is a factor of 1.4 104 more than that created by reaction with a 30 keV  γ-ray (see Fig. 2). Although this factor for 3He is larger (about 5.5 104), the neutron-γ  discrimination  for  BN  is  still  exceptional. Critical Issues: As with most semiconductor-based detectors, the key electrical properties for a successful device include: Carrier lifetime Carrier mobility Resistivity

In particular, the mobility-lifetime product is the distance a free charge carrier will travel, per unit applied electric field E, before capture, trapping, or recombination. [5] The distance E must therefore be on the order of the thickness d of the neutron reactive material (BN) for freed charge carriers to reach the device electrodes. Specific Goals for the Seed Project: The specific tasks of the seed project will be to calibrate the response of the propototype p-i-n detector to both thermal and fast neutrons from a Cf-252 source. This will be accomplished by performing pulse height analysis on the output pulses from an ultralow-noise cooled FET charge amplifier using a multichannel analyzer. This equipment is available in the PI’s lab. We will also perform mobility-lifetime measurements on the active BN layer of the detector. This will be accomplished using a unique ultrafast pump-probe laser spectrometer in the PI’s lab. The way this works is by exciting charge carriers in the active layer of the diode structure with a 100 femtosecond laser pulse and then, with a variable delay, to interrogate the response using a second ultrashort pulse. The resulting response curve reveals the relaxation of the charge carriers in the conduction band back to the valence band (or to traps) and from this response the mobility-lifetime product can be extracted. The timetable for these two main tasks will be approximately 12 months. The overall goal is to provide compelling performance data which will be the basis of a proposal to the detector programs of several federal agencies, including NNSA. The importance of these measurements is that the BN resistivity must be high enough that the background (dark) current is small compared to the current generated by the detection process. For example, for a BN-based p-i-n device of 1 μm  thickness,  1 cm2 area, and a dark current of 1 nA, the minimum required value of as a function of BN resistivity is shown in Fig.3. In addition, the electrical contact between the BN film and the device electrodes must be conducting enough that the free carrier current generated by the nuclear reaction is not blocked from flowing in the external measurement circuit. If the contact resistance is small compared to that of the BN, then essentially all of the electric field produced will be across the BN (and not across the BN/electrode interfaces), as needed to sweep out any free charge. [6] It is critical, therefore, for a BN- p-i-n device to have a combination of these key properties that satisfy the above requirements. An important research task for this seed effort then will be to evaluate these characteristics and to provide critical data that supports and strengthens our proposal to the NNSA and other interested agencies.

4

Figure 3. Minimum acceptable mobility-lifetime product versus BN film resistivity (with a dark current of  1  nA,  film  thickness  d  =  1  μm,   film area A = 1 cm2, and = t , the carrier transit time across the sample).

Infrastructure and Facilities: The PI has excellent facilities for this project, including a multitarget UHV ion beam sputter deposition system (for depositing metal contacts for BN- p-i-n devices), furnaces with inert gas flow (for annealing device contacts), a variety of standard instrumentation for characterizing the electrical properties of films, contacts, and devices, and custom instrumentation for carrier mobility measurement and neutron detection testing, including 2 ultralow-noise charge pulse amplifiers. A Californium 252 source fitted with a paraffin wax moderator is available for both fast and thermal neutron testing. Among the facilities most relevant to the proposed studies are a UHV ion-beam-assisted magnetron sputter deposition system [7] and a Menlo Systems femtosecond dual fiber laser for three-color pump-probe measurements of carrier lifetimes. The latter was purchased under DNDO-funded project CFP06-TA01-NS04. Also in the PI’s lab, and available to the project, are a Huber 4-circle x-ray diffractometer with an 18 kW rotating anode generator and a Nicolet FTIR spectrometer with reflection and transmission capabilities. In addition to these in-house facilities, Clarke is a frequent user of the Advanced Photon Source (APS) at Argonne National Laboratory, a premier source of high-brightness x-ray beams (see http://www.aps.anl.gov/Sectors/Sector7/ ). The University of Michigan Electron Microbeam Analysis Laboratory (EMAL) provides a broad spectrum of analytical and nano-mechanical testing equipment, including several Focused Ion Beam facilities, AFMs, and several high-resolution transmission electron microscopes (see http://www.emal.engin.umich.edu ). Another key shared UM facility is the Lurie Nanofabrication Facility (LNF), a modern microelectronics fabrication facility consisting of extensive class 10, class 100, and class 1000 work areas. LNF contains complete facilities for the fabrication and testing of Si and III-V based devices and circuits (see http://www.eecs.umich.edu/lnf/ ). LNF was used to construct the prototype p-i-n diode detector described in this seed proposal. Students to be supported: The seed project proposed here supports the stipend of one Graduate Student Research Assistant, who is an underrepresented student who has just successfully completed Rackham’s  “Bridge  to  the  PhD”  program  and  was  admitted  to  the Applied Physics PhD program in December 2013. His tuition will be covered by the Rackham RMF program. During the Bridge Program, this student worked with the PI becoming familiar with many of the measurement techniques and processes that are used in this detector project. He intends to make this project the topic of his doctoral dissertation project if funding is available. One undergrad REU student will also work on the project, supported by a supplement to the PI’s NSF grant. 5

Budget (12 month work performance period) GSRA Stipend (0.25) GradCare Benefits Total GSRA Stipend+GradCare

$14,508 4,062 $18,570

[Note: the other 0.25 component of the GSRA stipend will be covered by Rackham RMF support. This leverages the seed funding and also enables the student to develop an exciting dissertation topic, a win-win for the project and for the student] Other Costs Materials and Supplies Electronic components and data acquisition boards Wire bonding and electronic packaging Total Materials and Supplies LNF Fees (30 hours @ $40/hr) EMAL Fees (22 hours @45/hr) Total Seed Project Cost

6

$2,340 $1,580 $3,920 $1,200 $990 $24,680

ROY CLARKE - CURRICULUM VITAE Professor of Physics, Department of Physics, University of Michigan, 450 Church Street Ann Arbor, MI; Ph. (734) 764-4466; [email protected] EDUCATION B.Sc. (Physics) Queen Mary College, London, UK (1969) Ph.D. (Physics) University of London, 1973 PROFESSIONAL EMPLOYMENT Collegiate Professor of Physics, University of Michigan, 1986-present Director of the Applied Physics Program, University of Michigan, 1986 – 2002, 2009-2010 Associate Professor, Department of Physics, University of Michigan, 1982 -1986 Assistant Professor, Department of Physics, University of Michigan, 1979 - 1982 James Franck Fellow, University of Chicago, James Franck Institute, 1977-1979 Wolfson Fellow, Cavendish Laboratory, University of Cambridge, 1973 – 1977 Visiting Research Scientist, Indian Institute of Science, Bangalore, India, 1972 Science Research Council Co-operative Award in Science and Engineering, Allen Clark Research Center, Plessey Co., UK, 1969 -1973 HONORS AND AWARDS Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring, 2011 Royal Society Visiting Professorship (2010) Fellow of the American Physical Society Certificate of Appreciation for Outstanding Mentoring, A.P. Sloan Foundation, 2009 Imes-Moore Award for Graduate Student Mentoring, 2005 Marsden Foundation Bursary for International Collaboration, 2009 SYNERGISTIC ACTIVITIES Founded and directed University of Michigan Applied Physics Graduate Ph.D. Program. Member  of  the  “Bridge  to  the  PhD”  working  team,  American Institute of Physics. Co-founded k-Space Associates, Inc., Ann Arbor, MI. Co-founder of the Sector 7 beamlines for time-resolved x-ray scattering, Advanced Photon Source Chair of National User Organization of the Advanced Photon Source (1992 -1993). FIVE RELEVANT PUBLICATIONS (209 PUBLICATIONS TOTAL) 1. 2.

3. 4.

7

H. Sun, V. Stoica, M. Shtein, R. Clarke, and K. Pipe, Coherent Control of GHz Resonant Modes by an Integrated Acoustic Etalon, Phys. Rev. Letters 110, 086109 (2013). C.M. Schlepütz, Y. Yang, N.S. Husseini, R. Heinhold, H.-S. Kim, M.W. Allen, S.M. Durbin and R. Clarke, “The presence of a (1x1) oxygen overlayer on ZnO(0001) surfaces and at Schottky interfaces”,   J. Phys.: Condens. Matter 24, 095007 (2012). D. P. Kumah, S. Shusterman, Y. Paltiel, Y. Yacoby, R. Clarke, “Atomic-scale mapping of quantum dots  formed  by  droplet  epitaxy”, Nature Nanotechnology 4 835-838 (2009). V.A. Stoica, Y.-M Sheu, D.A. Reis, and R. Clarke, “Wideband detection of transient solid-state dynamics   using   ultrafast   fiber   lasers   and   asynchronous   optical   sampling,” Optics Express 16, 2322 (2008).

5. P.R. Willmott, S.A. Pauli, R. Herger, C.M. Schlepűtz, D. Martoccia, B.D. Patterson, B. Delley, R. Clarke, D. Kumah, C. Cionca, Y. Yacoby, “Structural  basis  for  the  conducting  interface  between   LaAlO3 and SrTiO3,” Phys. Rev. Lett. 99, 155502 (2007). FIVE OTHER PUBLICATIONS 1. E. Cohen, N. Elfassy, G. Koplovitz, S. Yochelis, S. Shusterman, D. P Kumah, Y. Yacoby, R. Clarke and Y. Paltiel, “Surface  X-ray diffraction results of the III-V dot droplet heteroepitaxy growth  process:  recent  understanding  and  open  questions”, Sensors 11, 10624 (2011). 2. Y. Li, V. Stoica, L. Endicott, G. Wang, C. Uher and R. Clarke, “Coherent optical phonon spectroscopy studies of femtosecond-laser modified Sb2Te3 films”, Appl. Phys. Lett. 97, 171908 (2010). 3. M.F. DeCamp, D.A Reis, A. Cavalieri, P.H. Bucksbaum, R. Clarke, R. Merlin, E.M. Dufresne, D.A. Arms, A.M. Lindenberg, A.G. MacPhee, Z. Chang, B. Lings, J.S. Wark, S. Fahy, "Transient strain driven by a dense electron-hole plasma," Phys. Rev. Lett. 91 165502 (2003). 4. Y. Yacoby, M. Sowwan, E. Stern, J. Cross, D. Brewe, R. Pindak, J. Pitney, E.M. Dufresne, R. Clarke, “Direct determination of epitaxial interface structure in Gd2O3 passivation   of   GaAs”, Nature Materials 1, 99-101 (2002). 5. H. Baltes, Y. Yacoby, R. Pindak, R. Clarke, L. Pfeiffer, L. Berman, “Measurement of the diffraction phase in a 2D crystal”, Phys. Rev. Lett. 79, 1285 (1997). COLLABORATORS (LAST 4 YEARS) R. Pindak (BNL), Y. Yacoby, (Hebrew University, Jerusalem), E. Stern (U. Washington), S. Durbin (SUNY Buffalo), P. Willmott (P.S.I., Switzerland), D. Schlom (Cornell), E. Dufresne (ANL), D. Reis (SLAC Stanford). GRADUATE AND POSTDOCTORAL ADVISOR: Prof. J.C. Burfoot (University of London, retired). Prof. A.D.Yoffe (Cavendish Lab., University of Cambridge). POSTDOCTORAL-SCHOLAR SPONSOR (LAST 5 YEARS)

F. Tsui (UNC Chapel Hill, NC), B. McNaughton (Life Magnetics Inc. /U. Michigan), A.R. Lukaszew (William and Mary); C. Schlepütz (Advanced Photon Source, Argonne National Lab). GRADUATE STUDENT ADVISOR H. Homma (Hyogo U., Japan), J. Gray (Ames Lab), M. Winokur (U. Wisconsin), P. Hernandez (U. Puebla, Mexico), B. Rodricks (ANL/APS), D. Grier (NYU), F. Lamelas (Worcester State), D. He (Blain Securities), Y. Sheng (Sun Microsystems), W. Dos Passos (U. Michigan), C. Cionca (U. Michigan), D. Medjahed (NIH, Bethesda), S. Elagoz (Sivas U., Turkey), J. Cunningham (Medtronic), S. Kidner (China Lake), C. Taylor (KSA Inc.), Peter Diehr (U. Michigan), E. Smith (LANL), J. Wellman (ANU, Canberra), D. Litvinov (U. Houston), G. Williams (Northrop-Grumman), W. Wang (Harvard), A. Daniel (Intel Corp.), P. Encarnación (Aerospace Corp.), D.P. Kumah (Yale),V. Stoica (U. Michigan); N. Husseini (U. Michigan). RECENT PATENTS Curvature/tilt metrology tool with closed loop feedback control [U.S. Patent No. 7,391,523 (2008)] Apparatus and method for real time measurement of substrate temperatures for use in semiconductor growth and wafer processing [U.S. Patent No. 7,837,383 (2010)]. Solid State BN Thin-film Neutron Detector [U.S. Patent No. 7,973,286 (2011)].

8

Bibliography

1. Glenn F. Knoll, Radiation Detection and Measurement, John Wiley &Sons (2010). 2. DNDO BAA06-02, ATD in Nuclear Detection Technology for Intelligent Personal Radiation Locators (2006). 3. W. C. McGinnis, R. Clarke, and C. Cionca, Film Implementation of a Neutron Detector (FIND): Critical Materials Properties, SSC San Diego Technical Report 1957 (Sep 2007); see http://www.spawar.navy.mil/sti/publications/pubs/trindex.html. 4. R. Clarke and C. Cionca, Solid State BN Thin-film Neutron Detector [U.S. Patent No. 7,973,286 (2011)]. 5. P. Stallinga, et al., Determining carrier mobility with a metal–insulator–semiconductor structure, Organic Electronics 9, 735 (2008). 6. G.W. Neudeck, The PN Junction Diode, 2nd ed., Addison Wesley (1989). 7. D. Litvinov, R. Clarke, C.A. Taylor II, and D. Barlett, Real-time strain monitoring in thin film growth: cubic boron nitride on Si (100), Mater. Sci. Eng. B66, 79 (1999).

9