Medium energy ion scattering and elastic recoil detection analysis for processes in thin films and monolayers Lyudmila V. Goncharova, Sergey Dedyulin, Mitch Brocklebank Department of Physics and Astronomy, Western University , London, Ontario, Canada Collaborators: P. J. Simpson (UWO), J. Botton (McMaster U.), D. Londheer (NRC)

1.7 MeV Tandetron Accelerator Facility at UWO Duoplasmatron Source Sputter Source Injector Magnet Tandetron Accelerator High Energy Magnet RBS Chamber ERD Chamber MEIS Chamber Implant Chamber Group III,V Molecular Beam Epitaxy System Group IV Molecular Beam

Energy distribution for one angle 2D MEIS Data 100keV H+, SiO2/poly-Si/ZrO2/Ge(100) H+ Energy [keV] Angle Energy distribution for one angle Angular distribution for one element Energy distributions: mass (isotope) specific quantitative (2% accuracy) depth sensitive (at the sub-nm scale)

Outline Motivation Medium Energy Ion Scattering (MEIS) - Nucleation and growth in Si and Ge quantum systems Medium Energy Elastic Recoil Detection (ME-ERD) - H-terminated Si(001) - H in HfSiOx ultra-thin films /Si(001) Conclusions and future directions

For the Age of Photonics… Continued developments in miniaturization, speed and complexity Wiring bottleneck Need to merge electronics and photonics III-V compounds dominate optoelectronics Hybrid technologies are being used OEICs and OICs incorporating Si/Ge detectors, modulators and waveguides now functional D.J. Paul, Semicond. Sci. Tech. 19, R75 (2009)

Overcoming the indirect band gap Alloying Ge with Si and/or C Stress Brillouin zone folding Rare earth and transition metal impurity centres Quantum confinement Wells (1-D) Wires (2-D) Dots (3-D) Band gap engineering

Experimental Approach Life-time decay Photoluminescence (PL) hn1 hn2 Ion beam implantation Tx, N2 Rutherford Backscat. (RBS) Elastic Recoil Detection (ERDA) Raman X-ray Photoemission Spec. *Stopping and Range of Ions in Matter, www.srim.org/ SRIM*

Growth and Analysis of Si QD RT Implantation Si- or Ge+ 90keV 5x1016 -1x1017ions/cm2 120min @11000C (Si) or 9000C (Ge) in furnace, 60 min @5000C in N2/H2 gas Early stage of formation governed by diffusion Eventually Ostwald ripening Link between defects in the SiO2 and formation of Si-QDs*

Ge QD Photoluminescense in Ge quantum systems Ge QD PL has two components: blue-green PL at ~2 eV (590 nm) independent of NC size near infrared PL size dependent, compatible with a QC effect Larger exciton radius (24 nm) compared with Si (~4nm) causes larger confinement effect in Ge QD Very challenging to fabricate a defect-free stable Ge QD!!! N.L. Rowell, et al., JES 156, H913 (2009)

Ge in Al2O3(0001): crystallization and ordering Ion beam implantation Tx, N2 Ge is moving up slow diffusion rate of the alumina matrix atoms at < Tmelt, significant crysllinity E.G. Barbagiovanni, et al., NIMB 272 (2012) 74–77

XPS Shift of Ge peak towards the surface (RBS) Al2O3(0001) GexO disordered Al2O3 Tx>1100oC N2 Al2O3(0001) Ge-QD Ar sputtering prior to XPS analysis: Ge layer is 3-5nm deep Shift of Ge peak towards the surface (RBS) GeOx peaks in XPS  Ge loss via GeO desorption

Cross-sectional TEM micrographs Moiré fringes become visible from the overlap of the crystal planes of Ge QD and the sapphire matrix Contrast arising from stress fields and end of range implantation damage

Ge QD in Al2O3(0001): MEIS vs HRTEM Slow diffusion rate of the alumina matrix atoms at < Tmelt Ge blocking minimum can be related to the stereographic projection of the sapphire crystal and corresponds to the [111] scattering plane: (1104) Al2O3 // (111)Ge and [211] Al2O3 // [112] Ge I.D. Sharp, Q. Xu, D.O.Y, et al., JAP 100 (2006) 114317

Outline Motivation Medium Energy Ion Scattering (MEIS) - Nucleation and growth in SI and Ge quantum systems Medium Energy Elastic Recoil Detection (ME-ERD) - H-terminated Si(001) - H in HfSiOx ultra-thin films /Si(001) Conclusions and future directions

Quantification in MEIS Scattering potential Cross section Neutralization RBS vs MEIS Normalized ion yield:   f+ changes as a function of energy and angle…

Missing element from the picture… hydrogen! Heavy Elements by MEIS or RBS “Classical” ERD Incident energy = 1.6MeV He+ Incident angle = 75o Recoil Angle = 30o Al-mylar (range foil) ~150nm SiONH/Si(001) Detector Light elements (He+ or H+) a Light Elements by Elastic Recoil Detection Detector He+ H+, He+ 

TEA detector for negative ions Crucial points for detecting H ion recoils directly are: To increase the recoil cross-section To reduce (to suppress) the background originating mainly from elastically scattered incident ions To reduce recoil energy V- V+ ME-ERD Only charged particles are detected by TEA  use incident beam ions without negative ion fractions and detect negative H- recoils V- V+ MEIS X+ H+,H, H-

Selection of Incident Ions Potential candidates: B, N, Ne, Na, Mg, Al, Si, P… Limitations: - possibility to produce these ions beam - high beam current - only H- are detected (fraction can be small) W.N. Lennard, et al. NIMB 179 (1981) 413

ME-ERD for H-Si(001) Incident beam: 500keV Si+ H- Incident angle = 45o Recoil Angle = 75o (TEA centre) Dose = 0.5mC Si+ H- Although the fraction of Si- ions is small, it is not negligible!

ME-ERD for H-Si(001) H- Si(001) vs H-Si(111) H- Si(001): assuming dihydride model  1.38x1015 /cm2 Sensitivity to H: 8x1013 H/cm2 Assuming that the normalized yield is 3500

H- Yield as a function of Si+ dose Irradiated area need to be refreshed! Si+ H- Without shifting irradiation area Compare with the sputter rates YH(I=0) = 984  ~ 30% of H is lost after 0.1mC Data shown below is without correction of H loss from the surface

ME-ERD for H-Si(001) H- Si(001) vs H-Si(111) H- Si(001): assuming dihydride model  1.38x1015 /cm2 Estimate of sensitivity to H: 8×1013 H/cm2 Extrapolated sensitivity to H: 1×1013 H/cm2 Assuming that the normalized yield is 3500

Angular dependence Best conditions at EH=2-5keV and angle = 70-80o observe angular dependence of H- fraction No H peaks at angles above 80o Low sensitivity at angles < 60o J.B. Marion, F.C. Young, NRA Tables, 1968. K. Mitsuhara et al., NIMB 276 (2012) 56-67

ME-ERD for Hf silicate films Incident beam: 500keV Si+ Incident angle = 45o Dose = 0.5mC Sample Tdep, C #cycles Thickness, nm In-situ RTA 1367 200 16 3.6 1351 300 19 UHV, 800oC, 30 sec 1355 350 21 3.4 1376 60 24

Summary: Towards “Complete ME-IBA” We were able to detect hydrogen using ME-ERD using Si(N) incident beams with no modification in TEA Medium Energy Elastic Recoil Spectroscopy with incident Si, N ions gives complimentary information on hydrogen content Hi-Si(001): we observe angular dependence of H- fraction The H- fraction is expected to increase with decreasing energy of the recoils (incident energy) Damage effects are significant  surface needs to be refreshed under the beam Uniform lateral distribution is assumed Accurate background fit is necessary to get quantitative fitting We were also able to detect residual hydrogen presence in Hf silicate thin films grown by atomic layer deposition with better resolution than “classical” ERD

Thank you!