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NATL INST OF STAND & TECH NiST PUBLICATIONS A111D7 DBHflMfl J ii Laboratory Physics J- SUPPORTING U.S. INDUSTRY, GOVERNMENT AND THE SCIENTIFIC COMMUNITY BY PROVIDING MEASUREMENT SERVICES AND RESEARCH. FOR ELECTRONIC, OPTICAL, AND RADIATION TECHNOLOGY Physics Laboratoryat a Glance Director's IVlessage 2 Electron and Optical Physics Division Atomic Physics Division 12 Optical TechnologyDivision., Ionizing Radiation Division 28 Time and Frequency Division 36 Quantum PhysicsDivision... 44 Office ofElectronic Commerce in Scientific and Engineering Data 52 Awardsand Honors 54 Organizational Chart 63 Physics Laboratory Resources.. 64 1 PHYSICS LABORATORY AT A GLANCE PLVision Quantum Physics Division: to make • Medical-Industrial Radiation Facility transformational advances at the frontiers (MIRF) Preeminentperformancein measurement ofscience, in partnershipwith the • Neutron Imaging Facility science, technology, andservices. UniversityofColorado atJILA. • Neutron Interferometerand Optics Facility (NIOF) PL Mission Office ofElectronicCommerce in • PrimaryOpticalWatt Radiometer Scientific and Engineering Data:to (POWR) The mission oftheNISTPhysics Labora- coordinate and facilitate theelectronic • Radiation DetectorTest Facility toryis to support U.S. industry, govern- dissemination ofinformationviathe • Radiopharmaceutical Standardization ment, and thescientificcommunityby Internet. Laboratory providingmeasurementservices and re- • Spectral Irradiance and Radiance PL Resources search forelectronic, optical, and radiation Calibrationswith Uniform Sources technology. TheLaboratoryprovides the 185 full-time staff(152 scientific] Facility (SIRCUS) foundation formetrologyofoptical and • Synchrotron Ultraviolet Radiation ionizing radiation, time andfrequency, with expertise in: Facility (SURF III) andfundamental quantum processes. • Atomic, molecular, and optical physics Standardtime dissemination services: PL Divisions • Computational physics WW,WWVH, • Condensed matterphysics • WRaWdiVoBstations and Physics Laboratoryis organized into six • Health physics divisionsthatareverticallyintegrated, with • Medical physics • Automated ComputerTime Service projects rangingfrom basic andapplied • Nuclearphysics (ACTS) research to measurementservices. Division • Biophysics • InternetTime Service (ITS) scientists collaboratewith oneanother, • Chemistry • TimeMeasurement andAnalysis with otherorganizationswithinNIST, • Metrologyand precision measurement Service (TMAS) andwith partners outside ofNIST in interdisciplinaryactivities relatedtohealth $75 million annual budget Measurementand calibration services care qualityassurance, nanotechnology, for: homelandsecurity, defense preparedness, Uniquefacilities, including: information technology, and environmen- • Colorand colortemperature tal and energyapplications. • Bidirectional Optical Scattering • Dosimetryofx rays, gammarays, and chargedparticles Facility Electron and Optical Physics Division: • Centerfor High-Accuracy • Neutron sources and neutron to support emergingelectronic, optical, Retroreflection Measurements dosimetry (CHARM) • Optical properties ofmaterials and nanoscaletechnologies. • Electron Beam IonTrap (EBIT) • Opticalwavelength Atomic Physics Division: to determine • Electron Paramagnetic Resonance • Oscillatorfrequency atomicproperties and investigate Facility • Phaseandamplitudenoise fundamentalquantum interactions. • EUVOptics Fabrication and • Photodiodespectral responsivity Characterization Facility • Photometry (e.g., luminous intensity, OpticalTechnologyDivision: to provide • High-Illuminance Standards and luminous flux, illuminance) the foundation foroptical radiation Calibration Facility • Radiance temperature measurements forourNation. • High-Resolution UVand Optical • Radiation detectors SpectroscopyFacility • Radioactivitysources Ionizing Radiation Division: to provide • W.M. KeckOptical Measurement • Spectral radianceand irradiance thefoundation ofionizingradiation Laboratory • Spectral transmittance and reflectance measurements forourNation. • Low-Background Infrared Radiation Time and Frequency Division: to provide Facility (LBIR) PL Website the foundation offrequencymeasurements • MagneticMicrostructure andcivil timekeepingforourNation. Measurement Facility http://physics.nist.gov/ • MammographicX-RayInstrument Calibration Range Message Director's ©Sam Kittner/Kittner.com This reportis intendedto provide notonly research can be just as challenging, base units oftime (the second), light (the an overviewofthe NIST Physics Laborato- cteative, and significantas "curiosity candela), andnoncontact thermometry ry's programs, but also asense ofthe range, driven," academicresearch. (the kelvin, especiallyabove 1200 K). We excitement, and relevance ofthe measure- provide the basis forsuch SI derived units ment science pursued in the Divisions. For example, ourTime and Frequency as thehertz (frequency), the becquerel (ra- Division's seven differentT&F services are dioactivity), and the opticalwattandthe In keepingwith the mission ofNIST, the supported bymajorefforts in the develop- lumen (light output). At thesame time, Laboratorysupports industry, government ofoptical frequencystandards, chip- scientists in the Physics Laboratorywork ment, and the scientificcommunitywith scale atomic clocks, andnext-generation with industryto develop newmeasurement measurement research andservices in cesium fountain atomic clocks, which ate technologies thatcan be applied to such electronic, optical, and ionizing radiation in turn supported byfundamental research fields as communications, microelectron- — technologies. Ourgreat strength and on trapped ions and neutral atoms. And ics, nanomagnetics, photonics, industrial what distinguishes us from an academic or just as ourworkon trapped ion clocks led radiation processing, the environment, — industrial laboratory is thatweareverti- to ourprogram in quantum information, health care, transportation, space, energy, callyintegratedwith abalanced portfolio so ourability to make quantum logic gates security, anddefense. ofprograms that span the full range from led to the developmentofthe quantum those thataddress the immediate needs logicclock. Similarly, the OpticalTechnol- Ourpartners are manyandouroutreach ofindustryto the more fundamental ogyDivision's workon next-generation extensive.JILA, ourjoint institutewith research that anticipates the future needs light detectors led to the creation ofsingle the UniversityofColorado, is nowin its ofindustry, government, and the scientific pairs ofphotons on demand, which is now 46"''year andstill gainingstaturewith three community. an integral part ofourprogram on quan- recent Nobel Laureates. Modeledloosely tum information. Likewise, the Ionizing onJILA, ournewJoint Quantum Institute The Laboratoryaddresses the fundamental Radiation Division is developinghighly (JQI) with the UniversityofMaryland triadofstandards, measurements, and data sensitive neutron detectors for homeland held its Inaugural Symposium on 27 in aclimate ofvigorous and competitive securityat the same time that it is using March 2007, an event notable for its high research.Justas the breadth, vigor, and ex- ultracold neutrons to investigate symme- concentration ofboth talent and enthusi- cellence ofourresearch programs provide tries and parameters ofthe nuclearweak asm. Followingin the same footsteps, our credibilityforourservices, so the increas- interaction. nascentJoint Biophysics Institutewith ingdemands forourservices provide a the UniversityofMaryland Biotechnol- strongandcrucial focus forourresearch Among our many responsibilities is the ogyInstitute is even nowformulatinga programs. The Physics Laboratoryhas maintenance ofthe U.S. national stan- Memorandum ofUnderstanding. At the ablydemonstrated thatmission-oriented dards for the Systeme International (SI) same time, the Physics Laboratorywas 2 Director'sMessage 3 honored bythe formerNIST Director's measurementorresearch, weform Over theyears, the Physics Laboratory's selection ofits Electron Physics Group, Cooperative Research and Development contributions have been recognized by led byRobert Celotta, to form the core of Agreements with industry. Laboratorysci- awards from industry, government, and aneworganizational unit, the Center for entists servewith distinction in standards- thescientific community, including 3 Nanoscale Science andTechnology. development committees and readilygive Nobel Prizes, 5 members ofthe National oftheir time to assist thepublic. AcademyofSciences, 1 MacArthur Fellow, The Laboratory places great importance on and47 Fellows oftheAmerican Physical determining, and focusingon, its highest Our talent is focusedon meetingtoday's Society. Some ofour recentawards and — priorityprograms. Foroptical radiation challenges in biosystems andhealth care, honors are listed in this report. measurements, we relyheavilyon the quantum technologies, and nanoscale Council for Optical Radiation Measure- metrology, to name butafew. Forhealth As you browse this summaryofthe Physics ments (CORM), formed to help define care, the Physics Laboratoryconducts Laboratory, we expectyouwillwant to pressing problems and projected national research on standards to enable hospitals learn more. We inviteyou tovisitourweb- needs in radiometryand photometry. Its to use nuclear medicine more effectively. site, http://physics.nist.gov/, andwe invite aim is to establish aconsensus on in- Wedevelopways to imagesingle biomol- your inquiries and interest in measurement dustrial andacademic requirements for ecules and to use terahertzradiation for services and collaborations. physical standards, calibration services, and measuringbiomolecular processes. The interlaboratorycollaborative programs in Physics Laboratoryis at the forefrontof the fields ofultraviolet, visible, and infra- the nascent fieldofquantum information — red measurements. Similarly, the Council processing computingand communica- — on Ionizing Radiation Measurements and tions challengingpreconceivednotions Standards (CIRMS) helps to advance ofcomputational complexityandcom- anddisseminate the physical standards munications security. Similarly, the Physics needed forthesafe and effective applica- Laboratoryhas been aleadingcenter for tion ofionizing radiation, includingx rays, metrologyat the nanoscale, even before gamma rays, and energetic particles such "nanotechnology" gainedprominence. We as electrons, protons, and neutrons. For pioneered electron-spin microscopy, which time and frequency, where the constitu- images magnetic materials, and our unique encyis lesswell defined, we use decadal EUVoptics facilitysupports the electronic surveys andcontactswith manufacturers of industryin its drive to develop advanced WWVB clocks and GPS receivers. When lithographicsystems forproducingever we can assistin an importantarea of smallerchips. and Electron Optical Physics Division GOAL To support emerging The strategyfor meeting thisgoal is to improve measurement science and to electronic, optical, and develop the measurements andstandards needed by emergingscience and nanoscale technologies technology-intensive industries. The ultraviolet), developmentoftechniques The Division's key tool for EUVmetrol- first strategic focus is the for fabricatingand characterizing EUV ogyis the NIST Synchrotron Ultraviolet development ofmetrology optical systems, andthe development ofa Radiation Facility (SURF III). SURF III, synchrotron-based, national primarystan- the successorto theworld's firstdedicated for extreme ultraviolet (EUV) optics, dard forsource-based optical radiometry. source ofsynchrotron radiation, is alow- energy (< 400 MeV), high beam-current the maintenance ofnational primary The Division has longstanding responsibil- (above 1 A), perfectlycircularelectron EUV ityfor the nationalprimary radiometric storage ring. Its operational characteristics standards for radiometryin the EUV EUV standards in the region ofthe spec- are ideal for metrology. Itdoes not and adjoiningspectral regions, and trum. EUV radiation is an important tool produce the hardx-ray radiation ofhigher fordetermining the electronicstructure of energysources, and it can beoperatedover the operation ofnational user facilities materials, diagnosingplasmas, measuring awide range ofbeam energies to match the dynamics ofthe upper atmosphere, and spectral response ofsystems ofinterest. As for EUVscience and applications. probing the structure anddynamics of acalculablesource ofradiation from the astrophysical objects. far infrared through EUVspectral regions, SURF is also used as aprimarystandard EXTREME ULTRAVIOLET One ofthe top candidates for next- forsource-based radiometry throughout generation semiconductor manufacturing the optical spectrum. RADIATION METROLOGY EUV technologyis an micropattern- ingtool, since operation atthis short a wavelength (13 nmvs. 193 nm forpresent, INTENDED OUTCOME AND production ultraviolet lithography) enables BACKGROUND diffraction-limited imagingoffeatures withsmaller critical dimensions. We are The intended outcomes ofthis program workingactivelywith the semiconductor are: maintenance andcontinuous improve- industryto develop new metrologyand mentofthe national primarymeasurement testingcapabilities as needs arise in their standards forextreme ultraviolet radiation effort to commercialize this next-genera- (EUV: wavelengths between4 nm and tion lithography. 250 nm, i.e., from softx rays tovacuum Electronand Optical Physics Division 5 ACCOMPLISHMENTS the ionosphere, due to the complete ab- prepared forphotoelectron emission imag- EUV sorption of radiation in the earth's ing and field emission microscopywere Calibration of the EUV upper atmosphere. observed in both imagingmodeswith Variability Experiment for submicron spatial resolution. NASA's Solar Dynamics The EVEpackagewas calibratedatSURF Observatory Mission III before its transferto NASAforincorpo- ration into SDO. Suc^h calibration is es- The SURF III facilityhas caHbrated sential for integratingEVE results into the everyextreme ultraviolet (EUV) spec- historical recordofsolarEUVvariability, trometer flown on NASA missions since andSURF III ispresentlythe onlyfacility the 1970s. In 2008, the first mission of in theworldthatcan provide this service. NASA's LivingWith a Star program is Fmiigcurroeg2r.ap[ah]sPoEfEaMcaarnbdon[b]nfaineoltdu-ebmeiseslieocntron scheduled for launch: the Solar Dy- Contact: Dr. Mitchell L. Furst emission device. namics Observatory (SDO). The SDO [301] 975-6378 mission will provide measurements [email protected] Itwas found thatlow-current emissionwas and models ofthe solar radiation and uniform and correlatedwith the photo- dynamics that can disturb Earth's space electron (PEEM) image. Hotspotswere weather environment. Electron Emission Properties of observed on some specimens that could be Graphene and Carbon Nanotube imaged simultaneouslyin PEEM and field emission microscopy. Metallized graphene Devices sheetswere foundto bevetygood emitters, Carbon nanotubes and nanosheets (gra- and the nature oftheiremission enhance- phene) are promisingcandidates forlow- ment is currentlyunderstudy. field, cold-electron emission devices, such as efficient electron sources anddisplays. Contact: Dr. Uwe Arp Lowthreshold fields are requiredto initiate [301] 975-3233 electron emission in thesesystems, on the [email protected] orderof1 mV/nm to 10 mV/nm. Figure 1.The EVEpackage inthecourseof a SURFIII calibration run. Here itis being This field strength is roughlythe same Record Beam Currents, loaded into a largevacuum chamberon as that used in photoemission electron Autonomous Operation, and SclUeRanFrIIIoboemamelnivniero2n,mewnhti.ch isenclosed in a microscopy sowe investigated the field- Royal Visit at SURF III emission and photoemissionproperties of SDO contains three instrument pack- carbon nanotubes and nanosheets, with Inlate2006, itbecamepossibleforthefirst ages, one ofwhich is the EUVVariability emphasis on the threshold field andthe timetoinjectcurrentsinexcessofanampere Experiment (EVE), built by the Labora- uniformityofemission. Typical nonimag- intotheSURFIIIelectronstoragering. toryforAtmospheric and Space Physics ingcharacterization focuses on the total WhenSURFIIfirstcameonlineinthemid- (LASP) ofthe University ofColorado. emittedcurrent. However, to optimize 1970s, itsmaximuminjectioncurrentswere EVE measures solar EUV irradiance deviceperformance, the entireemitter 10mA. Thesewereincreasedtoabout with unprecedented spectral resolution, structure must be active. 300mAbythetimeoftheconversionto temporal cadence, accuracy, and preci- SURF III in 1997, butthemaximumcur- sion. The EVE investigation program This motivated ourspatiallyresolved pho- rentsthencouldnotbegeneratedreproduc- incorporates physics-based models ofthe toelectron emission microscopy (PEEM) ibly.Awiderangeofimprovementsinthe solar EUVirradiance to advance the un- studies ofprototype devices producedby injectionandRFcontroltystems, carriedout derstanding ofthe solar EUV irradiance Prof Brian HoUowayatthe College of overthepastfiveyears, haveledtodetermin- variations based on the activity ofthe William and Maty. Thesestudieswerecar- isticinjectionconditions,whichgenerate solar magnetic features. Such variations riedout in collaborationwith Prof. Martin initialcurrentsthatareaslargeasthoseused have been found to have major effects on Kordesch ofOhio University, whilehe inanyothersynchrotronradiationsource. satellite drag and radio propagation in was on sabbaticalleave at NIST. Devices 1 6 NISTPhysics Laboratory SURF Status Display andisalso thesponsoringorganizationof Nanoscale Chemical III BeamCurrent asynchrotron radiation facility, SESAME, Imaging with Electron Beam 177.91mA ElectronEnergy whichis underconstructionthere. During Tomography 380.0 lUleV Lifetime RFVolta^B hertourofSURF III, PrincessSumayawas 7-20 h 28.15kV Orbitalradius offeredtheopportunityto injectabeam, and Tomographybecame an importantfield 837.0773mm RingVacuum carriedouttheprocedurequitesuccessfully. about40 years agowith the application F6.W3H8EM-X10FhWPaHMY 0179/:1001Time,0199/:100 1126/:1010 ofX rays to medical imaging. Thepractice 3.49mm2.00mm DoseRate Contact; Dr. Charles W. Clark quicklyspreadto electron microscopy. The 132.1B72 mmrAemh/h LasCtoumpmdeatnetd::A12U-TNOov-R2E0I0N7J1E6C:T00:20 [301] 975-3708 principal contrast mechanism inx-rayscat- Figure 3. SURFIII beam currentasafunc- [email protected] teringis absorptionwhich follows Beer's tion oftime, showing re-injections duringthe Law, i.e., the rule ofexponential attenua- nightinthe autonomous mode ofoperation. tion. Althoughitwas necessaryto develop Predicting the Lifetime of radicallydifferent algorithms fortomog- Furthermore, in 2007wewereabletoinsti- raphyusingmagnetic resonance imaging Extreme Ultraviolet Optics tuteregularautonomousoperationofthe orultrasound, theelectron microscopy facility,wherebyitautomaticallyre-injects Tohelpthesemiconductorindustrymeet communityimportedtheassumptionofa itselfwhenthebeamcurrentdecaystoapre- itsgoalofachievingextreme-ultraviolet probe travelinginastraightlinethrougha determinedtargetlevel. (Suchdecayoccurs lithography (EUVL) productionby2010, samplewith exponentialattenuation. duetoelectronsbeinglostfromthebeam wehaveestablishedadedicatedbeamlineat due to collisions.) Thisallowsforround-the- SURF III fordurabilitytestingofmultilayer This assumption isvalid forthinsamples, clockoperation,whichhasbeennecessaryto mirrors, anessentialunderlyingtechnology. but forthicksamples multipleelectron accommodategrowinguserdemand, particu- Thenewbeamlineisdevotedtoacceler- scatteringrenders itinvalid. Ourtheoreti- larlythatassociatedwithlifetimetestingof atedtesting, andwehaveaddedasecond cal analysis found thatnear theonsetof EUVopticalcomponents,which isdiscussed branchtoapreexistingbeamlinetoprovide multiple scattering (as thesamplethickness below. broadbandillumination (wavelengthsofap- underconsideration increases), there is a proximately 11 nmto 50 nm) ontoasingle regime inwhich the projectiveassumption spotatapproximately 100timestheintensity remainedvalid, but the transmission as a attainablebefore. function ofthickness deviatedsignificantly from Beers Law. Extensivenumericalsimu- Todeterminehowdamagescaleswithvari- lations confirmed this, attainingexcellent ousparameters,werecentlyexposedEUVL reconstructions ofan 8 pmsquaresample mirrors (providedbySEMATECH from ofaphotonic bandgap material usingthe workitco-ftmded) tovaiyinglevelsoflight multiplescatteringtransmission function. intensity,water, andhydrocarbonconcentra- tions. Contrarytoexpectations,wefound Figure4. HRH PrincessSumaya ofJordan thatincreasingamountsofwatervapor receives a certificate ofproficiencyin causedlessmirrordamage,whichmaybe synchrotronfacilityoperation from duetoasimultaneousincreaseintheambi- Dr. Katharine Gebbie. enthydrocarbonlevels. Subsequentexperi- Thesynchrotron radiation researchcom- mentshaveshownthatdeliberatelyintroduc- munityistight-knit, andmembersofthe ingtraceamountsofasimplehydrocarbon Figure 5. [a]Asynthetic photonic band SURF IIIstafffrequentlyinteractwith their likemethanolcanmitigatesignificantlythe gap structure, and (b] its reconstruction counterpartsatothersynchrotron facilities water-induceddamage. using Bayesiantomographyinthe multiple scattering regime. worldwide, hi May2007an unusualengage- mentofthistypeoccurredintheformof Contact: Dr. Thomas B. Lucatorto We used a Bayesian approach known as avisitbyaroyalpersonage, HRH Princess [301) 975-3734 thegeneralized Gaussian Markov random SumayaofJordan.ThePrincess istheheadof thomas.lucatortodinist.gov field, andextended it to treatsystemswith theRoyalScientificSocietyofJordan,which multiplescattering. The principal features containstheJordaniancounterpartofNIST, ofthis formalism are apriordistribution Electron and Optical Physics Division 7 based on correlations ofneighboringpixels The Division maintains two efforts in this (VCSELs), and the classical channel uses (orvoxels in 3D) inwhich the smoothness area, one theoretical and two experimen- 1550 nm light from normal commercial ofthe reconstruction maybe adapted to tal. The theoretical program is focused coarse wavelength division multiplexing the sample, andaquadraticapproximation on quantitative modelingofdegenerate devices.Apolarization auto-compensation to the logofthe likelihoodderived from quantum gases, with particularattention to module has been developed and utilized to Poisson statistics. In its original formula- the dynamics ofBose-Einstein condensates recover the polarization state and to com- tion, Beer's Lawwas also assumed. We subject to external fotces, e.g., manipula- pensate fortemporal drift. An automatic made a more general assumption: that tion ofcondensates confined in an optical timingalignment devicehas also been the transmission is anyknown function, lattice. This program is an outgrowth of developed to quickly handle the initial with sufficientdifferentiability, ofa linear extensive collaborationswith experimen- configuration ofquantum channels so that combination ofthe material parameters tal groups atNIST,JILA, andelsewhere, detection events fall into the correct timing ofthe sample. This has enabled us to begun in the mid-1990s. window. These automatedfunctions make gethighlysatisfactory reconstructions of the system more practical forintegration three-dimensional materials structure from The experimental programs are concerned into existing optical local area networks. limited angular samplingdata. with the application oflightstorage in and retrieval from atomic systems as a tech- We are developingafree-spaceoptical QKD Contact: Dr. Zachary H. Levine nique forquantum information process- system operatingatthe Balmer (301] 975-5453 ing, andthedevelopment ofhigh-speed alphawavelength of656 nm, where light zachary.levineOnist.gov quantum cryptography. from the sun is attenuated by7 dB in a narrow interval, which is advantageous QKD fordaylightoperation offree-space ACCOMPLISHMENTS systems. Weare also developingsemicon- The secondstrategic focus is ductoropticalwaveguides as asource of Quantum Key Distribution correlated photon pairs, in collaboration metrologyfor coherent matter- System Operating at a Sifted- with the Laboratoryfor Physical Sciences Key Rate Over 4 Mbit/s wave and quantum information ofthe UniversityofMaryland. We have collaboratedwithNIST'sAd- processingdevices. Contact: Dr. Joshua C. Bienfang vanced NetworkTechnologies Division in [301] 975-2105 developinga complete fiber-based, polar- [email protected] ization-encoded quantum keydistribution COHERENT MATTER- (QKD) system based on the Bennett-Bras- sard protocol (BB84). The system operates WAVE AND QUANTUM at aclockrate of1.25 GHz, and is capable 'March Madness' Effects INFORMATION ofproducingkeybits from quantum- Observed in Ultracold Gases channel transmissions (sifted key) at rates PROCESSING above 4 Mbit/s over 1 km ofoptical fiber. We have discovered newquantum phases in ultracoldgases thatreveal thecompeti- This output can be processed to produce METROLOGY unconditionallysecure cryptographic key tion between two major mechanisms of electrical resistance in solids: crystalline forencryptingmessages. disorder, and the interactions between INTENDED GUTCGME AND Our results represent a new record in the electrons. In "March Madness" terms, bas- QKD ketball fans who arrive earlyto an empty BACKGROUND operational outputrate ofa system stadium can move relativelyquicklydown basedon single-photon transmission. anyrow unless theyencounter a railing, This program provides measurements and Theyare made possible bythe integration wall, or otherbarrier (analogous to crystal data to enable thedevelopment ofultra- ofquantum cryptographyprotocolswith disorder). Butonce thegame begins, afan's cold atom technology, in particular the use classical high-speed telecommunications movements are constrained alongrows by ofcoherent matterwaves in sensors, atom techniques. The quantum channel uses interferometers, andquantum information 850 nm photons from attenuated high- other fans alreadyoccupyingseats (analogous to electron blocking). Even though processingdevices. speedvertical cavitysurface-emittinglasers 8 NISTPhysics Laboratory T PhillipAnderson and SirNeville Mott fhe third strategic focus is highspatial resolution (about 10 nm), long won Nobel Prizes in 1977 forthe theory workingdistance, andlargedepth-of-field ofthese phenomena in metals, ithas been to develop techniques for characteristicofSEM; anditfacilitates difficult to observe theireffects in real simultaneous measurements ofthe magneti- materials. fabricatingnanostructures and zation andthe topography. SEMPAstudies haveledto anumberofbreakthroughsin Quantum phases ofhard-core bosons con- measuring their electronicand understandingthebasic mechanismsof fined in a one-dimensional quasiperiodic magnetismon themicro-andnanoscale, magnetic properties. potentialwerestudiedwithin the theoreti- andhavealsoaddressed near-term measure- cal frameworkofintensityinterferometry mentissues facedbythemagneticdata (HanburyBrown-Twiss interferometry). storage industry. NANOSCALE The quasiperiodic potential induces a cas- cade ofMott-like band-insulator phases, in ELECTRONICS AND OurSTM program is focusedon un- addition to the more familiarMott insula- derstandingtheelectronicandmagnetic tor, Bose glass, and superfluid phases. The MAGNETICS properties ofnanostructuresonsurfaces. newphases are incompressible and have In recentyears theSTM program has been zero superfluid fraction. At critical filling particularlyconcernedwiththemagnetic factors, the appearance ofthese insulating INTENDED GUTCGME AND multilayermaterialsthathave been investi- phases is heralded bya peakto dip transi- BACKGROUND gatedbySEMPA. Thecomplementarities tion in the interferogram, which reflects ofSEMPAand STM measurements have the fermionic aspect ofhard core bosons. The intendedoutcome ofthisworkis the elucidated manyconnections betweencon- In the localized phase, the interference continuous improvementofmethods for ditionsoflayergrowth andmagneticdevice pattern exhibits ahierarchyofpeaks at the fabricatingandcharacterizingnanometer- performance. reciprocal latticevectors ofthe system. Our scaleelectronicandmagneticstructures, as studydemonstrates that, in contrast to requiredto meetcurrentand future needs Themain, currentdirection oftheSTM measurements ofthe momentum distribu- ofthesemiconductoranddatastorage program is thecourseofresearch madepos- tion, intensity interferometry provides an siblebythe recentlycompletedNanoscale industries. effective method to distinguish Mott and Physics Laboratory. This laboratorypermits glassyphases. Ourmain tools forpursuingthis program us to measurequantum electronicstructures arescanningelectron microscopywith with atomic-scale imagingresolutionand polarization analysis (SEMPA) andthe high electron-energyresolution. Samples scanningtunnelingmicroscope (STM). The grown insitucan be measuredinan ultra- Electron Physics Group in theDivisionhas highvacuumenvironmentwithmagnetic been aleadinginnovatorin bothofthese fields ofup to 10Tattemperaturesdownto methods, whichareoutgrowths ofworkbe- 2.3 K.Additionally, aprogram inAutono- Figure B. Representation ofthe interference gunatNISTin the 1970s. SEMPAenables mousAtomAssemblyis underwaythat ofwave patterns created byatomsthat usto useconventionalscanningelectron allows us to fabricatehighlycomplexand have been releasedfrom an optical lattice microscopy (SEM) to image nanometer- perfectnanostructuresondemand. with disorder.The complexshape ofpeaks andvalleys is an example ofa natural fractal scalemagneticstructure, throughspin- Theworkreportedbelowwas performedby pattern, a patternthatcontinuesto reveal polarization analysisofsecondaryelectrons newdetails no matterhowmanytimes itis ejectedfrom thesample. Ithas several theElectron Physics Group. In 2006, the magnified. uniquecapabilities thatdistinguish itfrom NISTDirectorselectedtheElectron Physics othermagnetic imagingtechniques: it is a Group toserveas the nucleus foranew highlysensitive, nonperturbative method, NISTCenterforNanoscaleScienceand Contact: Dr. Charles W. Clark Technology (CNST), whichwouldhave andthus isespeciallywell suited for insitu (301] 975-3708 studies ofsurfaceandnanostructure mag- primaryresponsibilityforactivitiesassoci- [email protected] netization; itprovides adirectmeasurement atedwith thenewnanofabricationfacility ofthe magnetization ofamaterial region, in theNISTAdvancedMeasurementLabo- ratherthanofamagneticfield; ithas the ratorycomplex. In May2007, CNSTwas