Imaging, Spectroscopy and Applications of Solid State Spins

1. Imaging, Spectroscopy and Applications of Solid State Spins Dr. KapildebAmbal kapildeb.ambal@nist.gov Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 Visiting fellow at National Institute of Standard Technology, Gaithersburg, Maryland 20899

2. Where are spins important? Qubits Quantum devices Flexible electronics Photovoltaic Motivation Solid state spins • How could we use spins? • What are solid state spins? Magnetometry Thermometry Nanoscience Nanoscale metrology Impurity atoms Vacancy centers Dangling bonds Localized states

3. What are solid state spins? Q Quantum well S Point defect is an imperfection that occurs at or around a single lattice point

4. = 1/2 ms= +1/2 Energy Q Measurement of solid state spins: electron spin resonance (ESR) ms= -1/2 Magnetic field S

5. - - - Free charge carriers Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] + + + + Measurement of solid state spins: electrically detected magnetic resonance (EDMR) dS dT Coherent spin manipulation PPS PPT Energy Spin-lattice relaxation kS - kT SE TE S0 E. L. Frankevich et al., Phys. Rev. B46, 9320 (1992). H. Malissaet al., Science345, 1487 (2014). T. D. Nguyen et al., Nature Mater. 9, 345 (2010). D. P. Waters et al., Nature Phys.11, 910 (2015). A. J. Schellekenset al., Phys. Rev. B84, 075204 (2011). cwEDMR signal with modulation

6. Metal contact _ _ _ + + External load Semiconductor Defects are costly: causing inefficiency Metal contact + Recombination _ _ _ _ _ _ _ Recombination Recombination + + + + + Thin-film technologies: CIGS CdTe Amorphous Si:H Emerging technologies: Organic solar cells Perovskite cells Quantum dot cells Defect mediated recombination of photo-induced charge carrier pairs

7. MOORE’S LAW Bad effects of solid state spins: device failure ~10 nm M. M. Waldrop, Nature 530, 144 ( 2016). Disadvantages:  Leakage current M. Xiao et al., Nature430, 435(2004).  Higher energy consumption  Low yield and device failure

8. Advantages of point defects: Quantum information science G. Popkin, Science354, 1091 (2016).

9. Benefits of point defects: Quantum sensing

10. SET ISET Methods for detecting individual spins time A. Morelloet al., Nature467, 687 (2010). Optically detected magnetic resonance A. Gruber et al., Science 276, 2012 (1997). D. Ruger et al., Nature, 430, 329 (2004).  Best spatial resolution from the existing single spin detection schemes is ~30nm.

11. How to measure physical properties of solid state spins? • Single-spin force microscopy • Development of Spin Probe • Imaging silicon dangling bonds • How could we use point defects in our favor? • Robust absolute magnetometry • Real-time magnetometry using NV- centers in diamond Outline

12. Electrostatic detection of single electronic charge V Single electron Tunneling event J P Johnson et al., Nanotechnology 20 055701 (2009). E. Bussmann et al., Nano Letters6, 2577 (2006). E. Bussmann et al., Appl. Phys. Lett.85, 2538 (2004).

13. Atomic spatial resolution • Electrostatic force >> dipolar force _  Possibly room temperature Concept of single-spin force microscopy • Highly sensitive ~ 10-2 e/ Vacuum gap _ Dielectric Dielectric tip A. Payne, K. Ambal, C. Boehme, and C. C. Williams, Phys. Rev. B91, 195433 (2015).

14. Spin dependent single electron charge tunneling noise Frequency shift Time Random tunneling signal  How spin resonance information will be extracted from charge tunneling?

15. Single occupied state Electron tunneling Spin selection rule and random tunneling noise spectroscopy rtunnel rate rflip rate X Electron tunneling OFF resonance ON resonance A. Payne, K. Ambal, C. Boehme, and C. C. Williams, Phys. Rev. B91, 195433 (2015).

16. Simulated resonance curves Viability of single electron spin resonance microscopy A. Payne, K. Ambal, C. Boehme, and C. C. Williams, Phys. Rev. B91, 195433 (2015).

17. Challenges: • Making spin probe with single spin at the end of it • Having a substrate with isolated spins • Aligning two spins with sub-nanometer precisions Challenges in single electron spin resonance force microscopy A. Payne, K. Ambal, C. Boehme, and C. C. Williams, Phys. Rev. B91, 195433 (2015).

18. How to measure physical properties of point defects? • Single-spin force microscopy • Development of Spin Probe • Imaging silicon dangling bonds • How could we use point defects in our favor? • Robust absolute magnetometry • Real-time magnetometry using NV- centers in diamond Outline

19. Long T1 (~200 μs) possibly at room temperature. “Crystalline Silicon – Properties and Uses”, ISBN 978-953-307-587-7 • Highly localized (~few Å). SiO2 Silicon • Compatible with silicon AFM probe. P. Lenahan and J. Conley, J. Vac. Sci. Technol. B 16, 2134 (1998). S. Eaton and G. Eaton, J. Magn. Reson. Ser. A102, 354 (1993). Preparation of spin-probe using E’ center Electron spin resonance  E’ center, a point defect in SiO2 SiO2/c-Si:P [E’] = 6x1018 cm-3 K. Ambalet al., Phys. Rev. Applied4, 024008 (2015).  Average distance of E’ centers ~7nm.

20. SiO2 Silicon Depth profile of E’ centers E’ distributed uniformly over 40nm. K. Ambal, A. Payne, C. C. Williams and C. Boehme, Phys. Rev. Applied 4, 024008 (2015).

21. Stability: thermal, optical, and temporal Eact = 176(1) meV Density decays exponentially due to thermal annealing. Density reduced significantly due UV light bleaching. Half life about a month at ambient condition. K. Ambal, A. Payne, C. C. Williams and C. Boehme, Phys. Rev. Applied 4, 024008 (2015).

22. B0 signal Relaxation time (T1) of high density E’ center time • T1 = 0.62(5) ms at 5K and estimated 0.195(5) ms at 300K . Summary of spin probe • E’ center suitable for probe spin. • It is stable at high density. • T1 is long at room temperature. K. Ambal, A. Payne, C. C. Williams and C. Boehme. Phys. Rev. Applied 4, 024008 (2015).

23. How to measure physical properties of point defects? • Single-spin force microscopy. • Development of Spin Probe • Imaging silicon dangling bond  How localized are dangling bonds? • How could we use spins in our favors? • Robust absolute magnetometry • Real-time magnetometry using NV- centers in diamond Outline

24. Conduction-AFM Imaging of individual dangling bond K. Ambalet al., Sci. Rep. 6, 18531 (2016).

25. V2 V1 Comparison with energy distribution of Pb centers K. Ambalet al., Sci. Rep.6, 18531 (2016). Gary J. Gerardi et al.,Appl. Phys. Lett. 49, 348 (1986) J. P. Campbell and P. M. Lenahan, Appl. Phys. Lett.80, 1945 (2002)

26. Concept of single-spin detection scheme. A. Payne, K. Ambal, C. Boehme, and C. C. Williams, Phys. Rev. B91, 195433 (2015). Conclusions : Single spin force microscopy • Developed a method to create probe spin. K. Ambalet al., . Phys. Rev. Applied 4, 024008 (2015). • Imaged of silicon dangling bond. K. Ambalet al., Sci. Rep.6, 18531 (2016).

27. Where are spins important? Outline How do we measure individual spins? What are solid state spins? Solid state spins How could we use spins? • Magnetometry

28. - - - Free charge carriers Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] + + + + Measurement of solid state spins: Electrically detected magnetic resonance (EDMR) dS dT Coherent spin manipulation PPS PPT Energy Spin-lattice relaxation kS - kT SE TE S0 E. L. Frankevich et al., Phys. Rev. B46, 9320 (1992). H. Malissaet al., Science345, 1487 (2014). T. D. Nguyen et al., Nature Mater. 9, 345 (2010). D. P. Waters et al., Nature Phys.11, 910 (2015). A. J. Schellekenset al., Phys. Rev. B84, 075204 (2011). cwEDMR signal with modulation

29. Absolute magnetometry with organic thin-film devices US Patent 9,551,772 • Calibration free • Absolute magnetic field sensing • Highly sensitive < 1 μT/ Hz1/2 • Thin film device • Low manufacturing cost • Temperature independent • Not Suitable for nanoscale magnetometry W.J. Baker, K. Ambal, D.P. Waters, R. Baarda, H. Morishita, K. van Schooten, D.R. McCamey, J.M. Lupton & C. Boehme, Nat. Comm. 3, 898 (2012).

30. How to measure physical properties of point defects? • Single-spin force microscopy. • Development of Spin Probe • Imaging silicon dangling bonds • How could we use point defects in our favors? • Robust absolute magnetometry • Real-time magnetometry using NV- centers in diamond Outline

31. Motivation: NV center magnetometry • Atom-size  near-ultimate spatial resolution (~10 nm) • Highly sensitive  10 nT/Hz1/2 • Works at room temperature Optically detected magnetic resonance (ODMR) 2γB0 • What problem do we solve? • Discrete photon  continuous signal • Peak locking • Peak tracking • Real-time magnetometry

32. Experimental setup Counter B0 K. Ambalet al., Rev. Sci. Instrum. 90, 023907 (2019). Provisional patent application no. 62/702129.

33. cw-ODMR: counter vs ratemeter Optically detected magnetic resonance (ODMR) K. Ambalet al., Rev. Sci. Instrum. 90, 023907 (2019). Provisional patent application no. 62/702129.

34. Frequency-modulated cw-ODMR Laser power ~300 µW PL ≈ 800 photons/ms fmod = 500 Hz Sensitivity: 4.1 µT/Hz1/2 K. Ambalet al., Rev. Sci. Instrum. 90, 023907 (2019). Provisional patent application no. 62/702129.

35. Continuous magnetometry via peak tracking K. Ambalet al., Rev. Sci. Instrum. 90, 023907 (2019). Provisional patent application no. 62/702129. Magnetometry without measuring and post-processing the data

36. Conclusions: magnetometry • Absolute magnetometry using organic thin film device W.J. Baker et al., Nat. Comm. 3, 898 (2012). • Differential/phase sensitive measurement using discrete photon pulses • Continuous tracking magnetic resonance over broad field range K. Ambalet al., Rev. Sci. Instrum. 90, 023907 (2019)

37. Where are spins important? Quantum information science Quantum sensing Nano-scale metrology Material characterization Efficient photovoltaic devices Summary • How do we • measure spins? • How could we use spins? Force microscopy Electron spin resonance (ESR) Electrically detected magnetic resonance (EDMR) Optically detected magnetic resonance (ODMR) Magnetometry Thermometry Nanoscience Nanoscale metrology Solid state spins • What are solid state spins? Impurity atoms Vacancy centers Dangling bonds Localized states

38. Quantum computing Solar technologies Outlook Quantum sensing Flexible electronics

39. Acknowledgement #DMR11-21252 National Science Foundation (Division of Materials Research) #0959328 Army Research Office #W911NF-10-1-0315

40. Thank you

42. c-Si without SiO2 Electrical detection and imaging of individual phosphorus Conduction-AFM FWHM ~ 20nm K. Ambal et.al., Sci. Rep. 6, 18531 (2016).

43. [31P] = 5 x 1014 cm-3 = 3 x 1017 cm-3 = 5x1018 cm-3 Phosphorus donor image at different concentration

44. Morphology (STM) c-AFM Surface morphology and phosphorus donor images

45. Electrical detection and imaging of silicon dangling bond K. Ambal et.al., Sci. Rep. 6, 18531 (2016).

46. I-V curves on individual silicon dangling bonds

47. Comparison of I-V spectroscopy with 31P-Pb center in c-Si/SiO2

48. Comparison of I-V spectroscopy with 31P-Pb center in c-Si/SiO2

49. Comparison of I-V spectroscopy with 31P-Pb center in c-Si/SiO2

50. Comparison of I-V spectroscopy with 31P-Pb center in c-Si/SiO2