Jesionek, M.

Kozlowski, Gregory

Nowak, Marian

Solecka, B.

English

CORE

Wright State UniversityCORE ScholarSpecial Session 5: Carbon and Oxide BasedNanostructured Materials (2013) Special Session 56-2013Photo-Electro-Magnetic or Photo-Thermo-Magneto-Electric Effects in Graphene?Marian NowakGregory KozlowskiWright State University - Main Campus, gregory.kozlowski@wright.eduB. SoleckaM. JesionekFollow this and additional works at: https://corescholar.libraries.wright.edu/ss5_2013Part of the Physics CommonsThis Presentation is brought to you for free and open access by the Special Session 5 at CORE Scholar. It has been accepted for inclusion in SpecialSession 5: Carbon and Oxide Based Nanostructured Materials (2013) by an authorized administrator of CORE Scholar. For more information, pleasecontact corescholar@www.libraries.wright.edu, library-corescholar@wright.edu.Repository CitationNowak, M., Kozlowski, G., Solecka, B., & Jesionek, M. (2013). Photo-Electro-Magnetic or Photo-Thermo-Magneto-Electric Effects inGraphene?. .https://corescholar.libraries.wright.edu/ss5_2013/4      Photo-electro-magnetic  or   photo-thermo-magneto-electric effects  in  graphene ?  M. Nowak1, G. Kozlowski2, B. Solecka1, M. Jesionek1 1 Silesian University of Technology, Katowice, Poland.2 Wright State University, Dayton, Ohio, USA.Photoelectromagnetic              E M  PEM photodetectors Series PEM-I uncooled detectors RV> 0.3 V/W for 1x1 mm2 optical area, with D*> 3·107 cmHz1/2/W.   Photo-electro-magnetic Photo-magneto-electric          illumination semiconductor electricresponsemagnetic field photo-magneto-electric effect        First-order PEM effect discovered in 1934by I. K. Kikoin and M. M. Noskov in CuO2                  bb’first-order PEM effect (a-a’) second-order PEM effectdiscovered by I.K Kikoin (1934)even PEM effect ~ 𝑩𝟐        Photogeneration of free carriersRecombinationDiffusion    first-order PEM effect            PEM currentmetal  electrodemetal  electrodefirst-order PEM  effect in open-circuit electricconductivitycurrenta bulk semiconductor      first-order  PEM effectodd PEM effect             𝒋𝒆 = 𝒆𝝁𝒆𝒏𝒆𝑬 + 𝒆𝑫𝒆𝒈𝒓𝒂𝒅 𝒏𝒆 , 𝝁𝑯𝒆 𝒋𝒆 × 𝑩	𝒋𝒉 = 𝒆𝝁𝒉𝒏𝒉𝑬 , 𝒆𝑫𝒉𝒈𝒓𝒂𝒅 𝒏𝒉 + 𝝁𝑯𝒉 𝒋𝒉 × 𝑩	𝝏𝒏𝒆 𝟏= 𝑮𝒆 , 𝑹𝒆 + 𝒅𝒊𝒗 𝒋𝒆𝝏𝒕 𝒆 𝝏𝒏𝒉 𝟏 = 𝑮𝒉 , 𝑹𝒉 , 𝒅𝒊𝒗 𝒋𝒉𝝏𝒕 𝒆                 𝑮𝒆 = 𝜷𝒆𝜶𝑰v(𝒚) 𝑮𝒉 = 𝜷𝒉𝜶𝑰v(y) 𝜶𝒆 𝜶𝒉𝜷𝒆 = 𝜼 𝜷𝒉 = 𝜼𝜶 𝜶 𝜶 = 𝜶𝒍 𝒍 𝒏𝒆,𝒏𝒆𝟎 𝒏𝒉,𝒏𝒉𝟎𝑹𝒆 = 𝑹𝒉 = 𝝉𝒆 𝝉𝒉                                                     Boundary conditions:𝑗𝑒𝑦 = 𝑒𝑠1𝑒∆𝑛𝑒 = 𝑒𝑠1ℎ∆𝑛ℎ for 𝑦 = 0	𝑗𝑒𝑦 = ,𝑒𝑠2𝑒∆𝑛𝑒 = , 𝑒𝑠2ℎ∆𝑛ℎ for 𝑦 = 𝑤𝑗	   𝒘𝒋 = 𝑩𝒍𝒛 𝒋𝒆𝒚𝒅𝒚𝝁𝑯𝒆 + 𝝁𝑯𝒉 𝒊𝑷𝑬𝑴 𝟎         𝒏𝒉𝝉𝒆𝜷𝒆+𝒏𝒆𝝉𝒉𝜷𝒉 =𝜷𝑷𝑬𝑴 𝒏𝒉𝝉𝒆+𝒏𝒆𝝉𝒉 =𝑳𝑷𝑬𝑴 𝑫𝝉𝑷𝑬𝑴	𝑺𝟏 = 𝒔𝟏𝒆𝝉𝒆𝒘𝟏 𝟐𝑳𝑷𝑴 𝒘𝟏𝑾 = 𝑳𝑷𝑬𝑴 𝟐𝑺𝟐 = 𝒔𝟐𝒆𝝉𝒆𝒘𝟏 𝑳𝑷𝑴            electropolished sample mechanically polished Numerical fitting of PEM responses on magnetic fieldValue o f parameter Fitted Initial E M a, (m3 0 - 1) a2(m4v-2s-2) I 0.01 (l.94 + 0.01) x 106 121.0 + 0.6 (5.29 + 0.01) x 106 134.0 + 0.4 a3 a4 12.3 0.011 [ 10 - 8] 0.715 + 0.003 as 0.011 a6 a~(Am- 1 ) 1400 0 - (5.5 + 1.5) x 10- s - (0.63 + 0.02) x 10- s   Real and imaginary parts of refractive index of a semiconductor illuminated with linearly polarized radiation (electric field normal to 𝑩 ) vs magnetic fieldPEM response due to the change refractive index in magnetic field (p and s refer to linearly polarized radiation with electric field normal and parallel to B)              a(l) wn-Geelectropolished samplemechanically polishedgrindedNumerical fitting of PEM current spectrum Value of the parameter 1 2 3 a + 1 59.l ± 1.1 161.0 ± 5.7 52.3 + 2.2 ( I) ( I) ( I ) 02 5.99 ± 0.12 5.95 + 0.67 3.35 ± 0.14 (10) (10) (10) al [ 31.4 ± 1.3) 193 + 10 ( I) (10) (JOO) 04 2.3 + 1.4 [ 13.0 ± 0.8] ( I) (1) (I) = W, a2       1.75 2.00 2.25 2.50 2.75012345 upem100UFME [ 10-5  V ]h [ eV ]0.00.20.40.60.8 tT   𝑽 𝑷𝑬𝑴 GaSeSpectral dependences of PEM voltage and optical transmittance (T)     Scheme of radiation propagation in a multilayer structure of a semiconductor and dielectric films.        w = 0.5µm. r 1. 2 OJ. ( \ \ ( \\ / ( I \ I X" i I \ I . ·, .!' \ ; i I / '. o .8 'y/ \ ; \ I '. I ' I \ I I /\ \ I "\ ,Ii l ; ' I ' I I \ \ I \ I \ _/ \ ) \ / "--. 02 µm: ""'------- 80 µ1n -'-------0 D.2 0.4 0.6 0.8 1 Y/W Spatial distribution of radiation intensity in a semiconductor for different thicknesses of the sample (InSb, l = 6.6 mm)                      Voltage responsivity of a thin-film PEM detector vs semiconductor thicknessfor different carrier lifetime and absorption coefficient. The dashe curverepresent the case of negligible internal reflection of radiation (1-t=3 ns, a=3104 m-1; 2-10 ns, 3104 m-1; 3- 3 ns, 105 m-1])          SiO2/p-Si SiO2/p-Si Numerical fitting of PEM responses to determine refractive index           1 UJ <JI (l. > "-.. ~ UI Q. a. > 3 ~ 2 ~ • • • • •• I . . . - 800 -• • • • • " • ' ~ . . ' 0 +800 U ( V J 8> •• • • • • • ..... .... Cl.I • c • • 4 ... -• • • ••• l .. ' . . . . . -BOO 0 '" •aoo · U(V) • FtG. 4.4. Ratio of PEM responses of p-type Si covered with natural oxide film illuminated with plane-polarised radiation with the electric vector in (p) and normal to (s) the plane of incidence versus electric field applied perpendicularly to the illuminated sample surface (0 = 60°, A. = 0.6328 µm, B = l.5 T). Real part of refractive index of p-type Si covered with natural oxide film vs electric field applied perpendicularly to the illuminated sample surface              20 30 40 50 60 70 80 90 1000.40.50.60.70.80.91UFME [ j.w. ], IFME [ j.w. ]f [ kHz ]te0Si:B=( 9.08 +/- 0.35 ) 10-7 s =(2.76 +/- 0.03 )10-6 sth0Normalised PEM () and PC  () responses vs frequency of illuminationintensity modulation (T=300 K; l=488 nm, Io= 31024 photons/(m2s) )                                     The PEM signal depends on:•	 gradient of concentrations of the photogenerated carriers, i.e.,- illumination intensity,- real part of refractive index of semiconductor,- absorption coefficient of light,- quantum efficiency coefficient for photogeneration of free carriers,•	 recombination rate, i.e.,- carrier lifetimes,- surface recombination velocity,• external magnetic field induction, • mobilities of carriers.                          PEM signal is stronger for higher mobilities ( me ) of carriers The suspended graphene devices showme = 6·105 cm2/(Vs)for n ø5.0·109 cm-2 at 77 K [N. Tombros (2011)].eHence, a premise for us to perform PEM investigations of graphene              Wavelength-independent optical absorption of 2.3 % per one atom thick graphene is significant [R.R. Nair et al. (2008),K. Mak et al. (2008)].𝒆𝟐 𝑻 ~ 𝟏 , 𝝅ℏ 𝒄            Band structure of graphene. (a) Dispersion relation under tight-binding approximation, (b) Dirac cones near Dirac point [Yamashita (2012)]Excitation process responsible forlinear optical absorption in graphene         Typical I-V curves of the graphene photodetector without and withlight excitation [F. Xia (2009)].                 Bilayer graphene gets a bandgap Stacking bilayer of graphene gives the possibility of tuning the energy gap and doping concentration by a vertical electric field(FET effect).Band gap can be tuned upto 250 meV [J. Nilsson et al. (2008)].                           Various mechanisms of recombination in graphene were considered, e.g.:•	 recombination due to Coulomb scattering (Auger recombination and impact ionization) [F. Rana (2007)], •	 recombination due to plasmon emission [F. Rana et al. (2011)],•	 recombination due to intravalley and intervalley opticalphonon scattering [F. Rana et al. (2009)], •	 recombination associated with the interband tunnelingbetween electron-hole puddles [V. Ryzhii et al. (2011)].The discussion is still open !                    Investigations of dynamics of photoexcited carriers in graphene:•	 femtosecond pump-probe measurements of opticalabsorption [J. H. Strait et al. (2011)], •	 time-resolved picosecond photocurrents measurements [L. Prechtel (2012)], •	 time-resolved photoemission spectroscopy [S. Gilbertsonet al. (2012)], •	 photoluminescence transients recorded by time-correlated single photon counting [T. Gokus et al. (2009)].The recombination of nonequilibrium electron-hole pairs yields to the observed white-light luminescence [R.J. Stöhret al. (2010)].                         Fast (100 fs) and slow (in hundreds of ps range) time constants to carrier-carrier and carrier-phonon intrabandand interband scattering processes in graphene.Theoretical calculations [V.N. Sokolov et al. (2011)] provided carrier lifetime in graphene of 0.1 ns at T=300 K (nø8.1·1010 cm-2) and 30 ns at Tø150 K (nø2·1010 cm-2). The high value of D=0.14÷0.30 m2/s was measured in graphene at room temperature [C. Józsa et al. (2009)].            PEM method can determine very small carrier lifetimes (e.g., t=10-11 s in GaAs [K.D. Glinchuk et al. (1982)]) because PEM signal in some cases is proportional to 𝑳 = 𝑫𝝉, where D is the diffusion coefficient.     Configuration of ourexperiment              J. Frenkel (1935) proposed to measure magnetic flux evoked by the loops of current in PEM effect. J. Hlavka (1972) was the first to perform it, and to suggest such measurements as a contactless PEM method to determine semiconductor parameters.     Configuration of ourmeasurements                              1 1T L 1 1 [S. Tumanski, Induction coil sensors—a review, Meas. Sci. Technol. 18 (2007) R31–R46]                         Experimental setup (L - laser, ZL - laser controler, A- acusto-opticalmodulator, W – laser beam, M- beam splitter, N,S - steady magnets, C -measuring coil, P - sample, CR – vacuum chamber of optical cryostat, K -computer with IEEE-488 bus, V1,V2 - lock-in amplifiers, T- temperature controller, D – photodiode, F- shutter)                     Monolayer graphene films were grown by CVD processing on a cooper foil and transferred onto glass substrates (Graphene Supermarket). Graphene coverage was about 90 %. The polycrystalline graphene films were continuous, with occasional holes and cracks. Their thicknesses and quality were controlled by Raman spectroscopy.                                                                                        Neodymium magnets (B=0.35 T or B=0.45 T) with 2 mm diameter hole in one of them;Conventional LN2 optical cryostat. Temperature stabilized laser diodes biased with ITC510 (Thorlabs) laser diode controller : Roithner LaserTechnik: S9850MBA (l=980 nm, radiation output P=50 mW) QL68J6S (l =685 nm, P=50 mW), Sonyo: DL7032-001 (l =830 nm, P=100 mW),Thorlabs: RLT1300-50G (l =1300 nm, P=50 mW),RLT1060-100G (l =1060 nm, P=100 mW),RLT905-100GS (l =905 nm, P=100 mW),HL7851G (l =785 nm, P=50 mW), RLT650 (l =650 nm, P=200 mW). EG&G lock-in 5110 amplifier that controlled frequency (f=71 kHz) of laser beam chopping.Neutral density filters UV–NIR-FILTER-250–2000 nm (Quartzglas-Substrate, Oriel). Hamamatsu S3399 photodiode in short-circuit regime. Lake Shore Cryotronics 211 temperature monitor (T=294 K). The experimental set-up was computerized using IEEE-488 bus.                    0 100 200 30001234  VPEM , mVt , sa a a ab b bTime dependence of voltage responses in PEM contactless investigations of graphene for different illumination intensity (a- unilluminated sample; b- illuminated sample;  – I=Ioø2.6·1022 photon/(m2s); ▲ – I=0.52 I0;▼- I=0.1 I0 ; l=830 nm; T=294 K; B=0.35 T)       ~ 2 ... hv= 1 .37 eV :E w 1 a.. > hv= 1.17 eV _......,..-B1=0.35 T • • j hv = 0.95 eV 0 0 2 4 6 8 lo , 1022 photon/(m2s) Voltage responses in PEM contactless investigations of graphene vs. illuminationintensity for various photon energies     𝑹𝑽 = 𝑽𝑷𝑬𝑴 𝑰𝒐	Influence of photon energy on photosensitivity of graphene in PEM effect.                     𝑺𝒊𝒈𝒏𝒂𝒍	𝒑𝒉𝒐𝒕𝒐𝒏	𝒔 ∙ 𝒎𝟐	photon detectorthermal detectorInfluence of photon energy on responsivity of ideal thermal (T, blue line) andphoton (P, red curve) detectors of radiation).                          The electron-photon-phonon interaction is a major scattering mechanism to determine photogenerated carrier densities in graphene10 0.1100Photogenerated electron density Dne as a function of the radiation wavelength for different strengths of the radiation field F0 (T=150 K; n0ø5·1011 cm−2). The inset shows ne as a function of F0 (l=6.0 mm) [W. Xu et al. (2010)].                 The PEM signal should exist also for other mechanisms creating a carrier flux , e.g., inhomogeneous heating by the incident light.temperature gradient in a crystal Nernst-Ettingshausen effect                          The Nernst-Ettingshausen (NE) effect is proportional both to the local temperature gradient and the applied magnetic field:where QNE is the NE coefficient and B is applied magnetic field. The NE coefficient varies by several orders of magnitude in different materials ranging from about 7 mV ·K−1T−1 in bismuth up to 10−5 mV · K−1T−1 in some metals [I.A. Luk’yanchuk at al. (2010)].         When illumination of a semiconductor produces not only an effective temperature gradient but also a carrier density gradientphoto-thermo-magneto-electric effect (PTME) effect                                    Three components of electric current or voltage can be markedout:(1) A component caused by the usual, diffusive PEM effect evoked by the gradient of excess carrier concentration.(2) A component caused by the gradient of free carrier temperature due to strong interaction between photogenerated hot carriers and the equilibrium free carriers. (3) A component evoked by the existence of a small number of the photogenerated hot carriers which interact weakly with the equilibrium free carriers.                        Under an applied bias, the intraband transitions lead tophotogenerated carriers which in turn increase the conductancewhileheating induced by the radiation increases the local temperature and hence increases the resistance due to a reduced mean freepath of charge carriers (bolometric effect). Photoconductive and bolometric responses are dependent on the material properties such as absorption coefficient andthermal conductivity.           graphenegraphitePhotoresponse for l=1064 nm of the graphitic films (a)and graphene (b) [N. Kurra et al. (2013)]              Photoresponse for l=1064 nm of the graphene and graphitic filmswith respect to Raman I2D/IG and ID/IG ratios respectively (1, 2-bulk graphite; 3, 4 – transferred graphene by Scotch tape and CVD; 5, 6 –PMMA–graphene; 7, 8 – RHC–graphene).      hv = 1.91 eV ~ 2 hv = 1.17 eV .. a w 1 hv = 1.37 eV a. > B1=0.35 T 0 0 2 4 6 8 lo' 1022 photon/(m2s) Voltage responses in PEM contactless investigations of graphene vs. illuminationintensity for different magnetic fields          Influence of photon energy on photosensitivity of graphene in PEM effect (symbols - the data obtained from linear fit of the results presented in Fig. 3; Inset presents schematically spectra of ideal thermal (T, blue line) and photon (P, red curve) detectors of radiation).                   The oscillations of the PEM effect with increase of magnetic field can be due to:• Shubnikov–de Haas type oscillations,  • Gurevich-Firsov type oscillations,• resonant PEM effect,• magnetophonon oscillations.                 Calculated [Shirasaki et al. (2012)] Seebeck Sxx(T,eF) (red line) and Nernst-Ettingshausen Syx(T,eF) (green line) components of the thermopower tensor (T= 0.1 K, eF = 10.7 meV, m* = 0.067/mo).               In a quantizing magnetic field the probability of emission of an optical phonon by a photogenerated hot electrons has itshighest value when longitudinal optical phonon ℏ w𝟎 becameequal to the gap between the Landau levels ℏW , where W is the cyclotron frequency. This should give rise to magnetophonon oscillations of the PEM effect.           ICR = impurity cyclotron resonance ECR = electron cyclotron resonance The resonant PEM voltage and the absorption signal obtained by transmission experiment in n-InSb at 4.2 K [T. Okashita et al. (2001)].                                  Conclusions • New contactless and nondistructive technique for graphene study and characterization can use PEM orPTME effects.• Experiments are in progress.• Theoretical description of photothermomagnetoelectriceffect in graphene is needed.• Cooperation with other reserchers is valuable. Thanks for your attention 

Photo-Electro-Magnetic or Photo-Thermo-Magneto-Electric Effects in Graphene?

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Photo-Electro-Magnetic or Photo-Thermo-Magneto-Electric Effects in Graphene?

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