Dense Ge nanocrystal layers embedded in oxide obtained by controlling the diffusion–crystallization process

  • Ana-Maria Lepadatu
  • Toma Stoica
  • Ionel Stavarache
  • Valentin Serban Teodorescu
  • Dan Buca
  • Magdalena Lidia Ciurea
Research Paper


Amorphous Ge/SiO2 multilayer structures deposited by magnetron sputtering have been annealed at different temperatures between 650 and 800 °C for obtaining Ge nanocrystals in oxide matrix. The properties of the annealed structures were investigated by transmission electron microscopy, Raman spectroscopy, and low temperature photoluminescence. The Ge crystallization is partially achieved at 650 °C and increases with annealing temperature. Insight of the Ge nanocrystal formation was acquired by comparing two annealing procedures, i.e., in a conventional tube furnace and by a rapid thermal annealing. By rapid thermal annealing in comparison to conventional furnace one, the Ge crystallization process is faster than Ge diffusion, resulting in the formation of more compact layers of Ge nanocrystals with 8–9.5-nm size as Raman spectroscopy reveals. These findings are important to improve the annealing efficiency in the nanocrystals formation for a precise control of their sizes and location in oxide matrix and for the possibility to create systems with interacting nanoparticles for charge or excitonic transfer. The infrared photoluminescence of Ge nanocrystals at low temperatures shows strong emission with two sharp peaks at about 1,000 meV.


Ge/SiO2 multilayer structures Ge diffusion Ge nanocrystal formation TEM Raman spectroscopy Photoluminescence 



This study was performed partially under the auspices of the National Research Council—Executive Agency for Higher Education, Research, Development and Innovation Funding (CNCS—UEFISCDI), by funding projects No. PN II-PT-PCCA-9/2012 and No. PN II-RU-PD-2011/3/0094.


  1. Ağan S, Dana A, Aydinli A (2006) TEM studies of Ge nanocrystal formation in PECVD grown SiO2:Ge/SiO2 multilayers. J Phys Condens Matter 18:5037–5045. doi: 10.1088/0953-8984/18/22/004 CrossRefGoogle Scholar
  2. Ang R, Chen TP, Yang M, Wong JI, Yi MD (2010) The charge trapping and memory effect in SiO2 thin films containing Ge nanocrystals. J Phys D 43:015102. doi: 10.1088/0022-3727/43/1/015102 CrossRefGoogle Scholar
  3. Arguirov T, Mchedlidze T, Kittler M, Rölver R, Berghoff B, Först M, Spangenberg B (2006) Residual stress in Si nanocrystals embedded in a SiO2 matrix. Appl Phys Lett 89:053111. doi: 10.1063/1.2260825 CrossRefGoogle Scholar
  4. Buljan M, Desnica UV, Dražić G, Ivanda M, Radić N, Dubček P, Salamon K, Bernstorff S, Holý V (2009) The influence of deposition temperature on the correlation of Ge quantum dot positions in amorphous silica matrix. Nanotechnology 20:085612. doi: 10.1088/0957-4484/20/8/085612 CrossRefGoogle Scholar
  5. Chang JE, Liao PH, Chien CY, Hsu JC, Hung MT, Chang HT, Lee SW, Chen WY, Hsu TM, George T, Li PW (2012) Matrix and quantum confinement effects on optical and thermal properties of Ge quantum dots. J Phys D 45:105303. doi: 10.1088/0022-3727/45/10/105303 CrossRefGoogle Scholar
  6. Chew HG, Zheng F, Choi WK, Chim WK, Foo YL, Fitzgerald EA (2007) Influence of reductant and germanium concentration on the growth and stress development of germanium nanocrystals in silicon oxide matrix. Nanotechnology 18:065302. doi: 10.1088/0957-4484/18/6/065302 CrossRefGoogle Scholar
  7. Choi WK, Choo CK, Han KK, Chen JH, Loh FC, Tan KL (1998) Densification of radio frequency sputtered silicon oxide films by rapid thermal annealing. J Appl Phys 83:2308–2314. doi: 10.1063/1.366974 CrossRefGoogle Scholar
  8. Choi WK, Ho YW, Ng V (2001) Effect of size of Ge nanocrystals embedded in SiO2 on Raman spectra. Mater Phys Mech 4:46–50Google Scholar
  9. Das S, Singha RK, Manna S, Gangopadhyay S, Dhar A, Ray SK (2011) Microstructural, chemical bonding, stress development and charge storage characteristics of Ge nanocrystals embedded in hafnium oxide. J Nanopart Res 13:587–595. doi: 10.1007/s11051-010-0054-8 CrossRefGoogle Scholar
  10. Das S, Aluguri R, Manna S, Singha R, Dhar A, Pavesi L, Ray SK (2012) Optical and electrical properties of undoped and doped Ge nanocrystals. Nanoscale Res Lett 7:143. doi: 10.1186/1556-276X-7-143 CrossRefGoogle Scholar
  11. Foss S, Finstad TG, Dana A, Aydinli A (2007) Growth of Ge nanoparticles on SiO2/Si interfaces during annealing of plasma enhanced chemical vapor deposited thin films. Thin Solid Films 515:6381–6384. doi: 10.1016/j.tsf.2006.11.094 CrossRefGoogle Scholar
  12. Fujii M, Hayashi S, Yamamoto K (1991) Growth of Ge microcrystals in SiO2 thin film matrices: a Raman and electron microscopic study. Jpn J Appl Phys 30:687–694. doi: 10.1143/JJAP.30.687 CrossRefGoogle Scholar
  13. Gao F, Green MA, Conibeer G, Cho EC, Huang Y, Pere-Wurfl I, Flynn C (2008) Fabrication of multilayered Ge nanocrystals by magnetron sputtering and annealing. Nanotechnology 19:455611. doi: 10.1088/0957-4484/19/45/455611 CrossRefGoogle Scholar
  14. Hessel CM, Wei J, Reid D, Fujii H, Downer MC, Korgel BA (2012) Raman spectroscopy of oxide-embedded and-stabilized silicon nanocrystals. J Phys Chem Lett 3:1089–1093. doi: 10.1021/jz300309n CrossRefGoogle Scholar
  15. Hiller D, Goetze S, Zacharias M (2011) Rapid thermal annealing of size-controlled Si nanocrystals: dependence of interface defect density on thermal budget. J Appl Phys 109:054308. doi: 10.1063/1.3556449 CrossRefGoogle Scholar
  16. Huo Y, Lin H, Chen R, Rong YW, Kamins TI, Harris JS (2012) MBE growth of tensile-strained Ge quantum wells and quantum dots. Front Optoelectron 5:112–116. doi: 10.1007/s12200-012-0193-x Google Scholar
  17. Iwayama TS, Hama T, Hole DE, Boyd IW (2006) Enhanced luminescence from encapsulated silicon nanocrystals in SiO2 with rapid thermal anneal. Vacuum 81:179–185. doi: 10.1016/j.vacuum.2006.03.023 CrossRefGoogle Scholar
  18. Janicki V, Sancho-Parramon J, Zorc H, Salamon K, Buljan M, Radić N, Desnica U (2011) Ellipsometric study of thermally induced redistribution and crystallization of Ge in Ge:SiO2 mixture layers. Thin Solid Films 519:5419–5423. doi: 10.1016/j.tsf.2011.02.071 CrossRefGoogle Scholar
  19. Jie YX, Wee ATS, Huan CHA, Sun WX, Shen ZX, Chua SJ (2004) Raman and photoluminescence properties of Ge nanocrystals in silicon oxide matrix. Mater Sci Eng B 107:8–13. doi: 10.1016/j.mseb.2003.09.037 CrossRefGoogle Scholar
  20. Jie Y, Wee ATS, Huan CHA, Shen ZX, Choi WK (2011) Phonon confinement in Ge nanocrystals in silicon oxide matrix. J Appl Phys 109:033107. doi: 10.1063/1.3503444 CrossRefGoogle Scholar
  21. Kanemitsu Y, Masuda K, Yamamoto M, Kajiyama K, Kushida T (2000) Near-infrared photoluminescence from Ge nanocrystals in SiO2 matrices. J Lumin 87–89:457–459. doi: 10.1016/S0022-2313(99)00486-X CrossRefGoogle Scholar
  22. Kim S, Choi SH, Park CJ, Cho KH, Cho HY, Elliman RG (2006) Structural and optical characterization of Ge nanocrystals showing large nonvolatile memories in metal-oxide-semiconductor structures. J Korean Phys Soc 49:959–962. doi: 10.3938/jkps.49.959 Google Scholar
  23. Kolobov AV, Wei SQ, Yan WS, Oyanagi H, Maeda Y, Tanaka K (2003) Formation of Ge nanocrystals embedded in a SiO2 matrix: transmission electron microscopy, X-ray absorption, and optical studies. Phys Rev B 67:195314. doi: 10.1103/PhysRevB.67.195314 CrossRefGoogle Scholar
  24. Lieten RR, Bustillo K, Smets T, Simoen E, Ager JW, Haller EE, Locquet JP (2012) Photoluminescence of bulk germanium. Phys Rev B 86:035204. doi: 10.1103/PhysRevB.86.035204 CrossRefGoogle Scholar
  25. Maeda Y, Tsukamoto N, Yazawa Y, Kanemitsu Y, Masumoto Y (1991) Visible photoluminescence of Ge microcrystals embedded in SiO2 glassy matrices. Appl Phys Lett 59:3168–3170. doi: 10.1063/1.105773 CrossRefGoogle Scholar
  26. Mestanza SNM, Rodriguez E, Frateschi NC (2006) The effect of Ge implantation dose on the optical properties of Ge nanocrystals in SiO2. Nanotechnology 17:4548–4553. doi: 10.1088/0957-4484/17/18/004 CrossRefGoogle Scholar
  27. Nataraj L, Xu F, Cloutier SG (2010) Direct-bandgap luminescence at room temperature from highly-strained Germanium nanocrystals. Opt Express 18:7085–7091. doi: 10.1364/OE.18.007085 CrossRefGoogle Scholar
  28. Nilsson G, Nelin G (1971) Phonon dispersion relations in Ge at 80°K. Phys Rev B 3:364–369. doi: 10.1103/PhysRevB.3.364 CrossRefGoogle Scholar
  29. Niquet YM, Allan G, Delerue C, Lannoo M (2000) Quantum confinement in germanium nanocrystals. Appl Phys Lett 77:1182–1184. doi: 10.1063/1.1289659 CrossRefGoogle Scholar
  30. Ou H, Ou Y, Liu C, Berg RW, Rottwitt K (2011) Formation and characterization of varied size germanium nanocrystals by electron microscopy, Raman spectroscopy, and photoluminescence. Opt Mater Express 1:643–651. doi: 10.1364/OME.1.000643 CrossRefGoogle Scholar
  31. Pinto SRC, Rolo AG, Chahboun A, Kashtiban RJ, Bangert U, Gomes MJM (2010) Raman study of stress effect on Ge nanocrystals embedded in Al2O3. Thin Solid Films 518:5378–5381. doi: 10.1016/j.tsf.2010.03.035 CrossRefGoogle Scholar
  32. Pinto SRC, Rolo AG, Buljan M, Chahboun A, Bernstorff S, Barradas NP, Alves E, Kashtiban RJ, Bangert U, Gomes MJM (2011) Low temperature fabrication of layered self-organized Ge clusters by RF-sputtering. Nanoscale Res Lett 6:341. doi: 10.1186/1556-276X-6-341 CrossRefGoogle Scholar
  33. Richter H, Wang ZP, Ley L (1981) The one phonon Raman spectrum in microcrystalline silicon. Solid State Commun 39:625–629. doi: 10.1016/0038-1098(81)90337-9 CrossRefGoogle Scholar
  34. Rodríguez A, Rodríguez T, Prieto ÁC, Jiménez J, Kling A, Ballesteros C, Sangrador J (2010) Crystallization of amorphous Si0.6Ge0.4 nanoparticles embedded in SiO2: crystallinity versus compositional stability. J Electron Mater 39:1194–1202. doi: 10.1007/s11664-010-1254-9 CrossRefGoogle Scholar
  35. Roodenko K, Goldthorpe IA, McIntyre PC, Chabal YJ (2010) Modified phonon confinement model for Raman spectroscopy of nanostructured materials. Phys Rev B 82:115210. doi: 10.1103/PhysRevB.82.115210 CrossRefGoogle Scholar
  36. Sahin D, Yildiz I, Gencer AI, Aygun G, Slaoui A, Turan R (2010) Evolution of SiO2/Ge/HfO2(Ge) multilayer structure during high temperature annealing. Thin Solid Films 518:2365–2369. doi: 10.1016/j.tsf.2009.09.156 CrossRefGoogle Scholar
  37. Sasaki Y, Horie C (1993) Resonant Raman study of phonon states in gas-evaporated Ge small particles. Phys Rev B 47:3811–3818. doi: 10.1103/PhysRevB.47.3811 CrossRefGoogle Scholar
  38. Serincan U, Kartopu G, Guennes A, Finstad TG, Turan R, Ekinci Y, Bayliss SC (2004) Characterization of Ge nanocrystals embedded in SiO2 by Raman spectroscopy. Semicond Sci Technol 19:247–251. doi: 10.1088/0268-1242/19/2/021 CrossRefGoogle Scholar
  39. Srinivasa Rao N, Dhamodaran S, Pathak AP, Kulriya PK, Mishra YK, Singh F, Kabiraj D, Pivin JC, Avasthi DK (2007) Structural studies of Ge nanocrystals embedded in SiO2 matrix. Nucl Instrum Meth Phys Res B 264:249–253. doi: 10.1016/j.nimb.2007.08.094 CrossRefGoogle Scholar
  40. Stavarache I, Lepadatu AM, Gheorghe NG, Costescu RM, Stan GE, Marcov D, Slav A, Iordache G, Stoica TF, Iancu V, Teodorescu VS, Teodorescu CM, Ciurea ML (2011) Structural investigations of Ge nanoparticles embedded in an amorphous SiO2 matrix. J Nanopart Res 13:221–232. doi: 10.1007/s11051-010-0021-4 CrossRefGoogle Scholar
  41. Stavarache I, Lepadatu AM, Maraloiu AV, Teodorescu VS, Ciurea ML (2012) Structure and electrical transport in films of Ge nanoparticles embedded in SiO2 matrix. J Nanopart Res 14:930. doi: 10.1007/s11051-012-0930-5 CrossRefGoogle Scholar
  42. Stavarache I, Lepadatu AM, Stoica T, Ciurea ML (2013) Annealing temperature effect on structure and electrical properties of films formed of Ge nanoparticles in SiO2. Appl Surf Sci. doi: 10.1016/j.apsusc.2013.08.031
  43. Stoica T, Sutter E (2006) Ge dots embedded in SiO2 obtained by oxidation of Si/Ge/Si nanostructures. Nanotechnology 17:4912–4916. doi: 10.1088/0957-4484/17/19/022 CrossRefGoogle Scholar
  44. Takeoka S, Fujii M, Hayashi S, Yamamoto K (1998) Size-dependent near-infrared photoluminescence from Ge nanocrystals embedded in SiO2 matrices. Phys Rev B 58:7921–7925. doi: 10.1103/PhysRevB.58.7921 CrossRefGoogle Scholar
  45. Wan Z, Huang S, Green MA, Conibeer G (2011) Rapid thermal annealing and crystallization mechanisms study of silicon nanocrystal in silicon carbide matrix. Nanoscale Res Lett 6:129. doi: 10.1186/1556-276X-6-129 CrossRefGoogle Scholar
  46. Wang W, Wang K, Han D, Poudel B, Wang X, Wang DZ, Zeng B, Ren ZF (2007) Exciton states and photoluminescence in Ge quantum dots. Nanotechnology 18:075707. doi: 10.1088/0957-4484/18/29/295401 CrossRefGoogle Scholar
  47. Wellner A, Paillard V, Bonafos C, Coffin H, Claverie A, Schmidt B, Heinig KH (2003) Stress measurements of germanium nanocrystals embedded in silicon oxide. J Appl Phys 94:5639–5642. doi: 10.1063/1.1617361 CrossRefGoogle Scholar
  48. Wu RS, Luo XF, Yuan CL, Zhang ZR, Yu JB (2009) Dielectric matrix imposed stress strain effect on photoluminescence of Ge nanocrystals. Physica E 41:1403–1405. doi: 10.1016/j.ssc.2009.01.031 CrossRefGoogle Scholar
  49. Xiao H, Huang S, Zheng J, Xie G, Xie Y (2009) Optical characteristics of Si/SiO2 multilayers prepared by magnetron sputtering. Microelectron Eng 86:2342–2346. doi: 10.1016/j.mee.2009.04.014 CrossRefGoogle Scholar
  50. Ye CN, Wu XM, Tang NY, Zhuge LJ, Yao WG, Chen J, Dong YM, Yu YH (2002) Origin of photoluminescence peaks in Ge–SiO2 thin films. Sci Technol Adv Mater 3:257–260. doi: 10.1016/S1468-6996(02)00024-4 CrossRefGoogle Scholar
  51. Zhang B, Shrestha S, Green MA, Conibeer G (2010a) Size controlled synthesis of Ge nanocrystals in SiO2 at temperatures below 400 °C using magnetron sputtering. Appl Phys Lett 96:261901. doi: 10.1063/1.3457864 CrossRefGoogle Scholar
  52. Zhang B, Shrestha S, Aliberti P, Green MA, Conibeer G (2010b) Characterisation of size-controlled and red luminescent Ge nanocrystals in multilayered superlattice structure. Thin Solid Films 518:5483–5487. doi: 10.1016/j.tsf.2010.04.024 CrossRefGoogle Scholar
  53. Zhang B, Yao Y, Patterson R, Shrestha S, Green MA, Conibeer G (2011) Electrical properties of conductive Ge nanocrystal thin films fabricated by low temperature in situ growth. Nanotechnology 22:125204. doi: 10.1088/0957-4484/22/12/125204 CrossRefGoogle Scholar
  54. Zi J, Zhang K, Xie X (1997) Comparison of models for Raman spectra of Si nanocrystals. Phys Rev B 55:9263–9266. doi: 10.1103/PhysRevB.55.9263 CrossRefGoogle Scholar
  55. Zschintzsch M, Jeutter NM, von Borany J, Krause M, Mücklich A (2010) Reactive dc magnetron sputtering of (GeOx–SiO2) superlattices for Ge nanocrystal formation. J Appl Phys 107:034306. doi: 10.1063/1.3276184 CrossRefGoogle Scholar
  56. Zschintzsch M, Sahle CJ, von Borany J, Sternemann C, Mücklich A, Nyrow A, Schwamberger A, Tolan M (2011a) Ge–Si–O phase separation and Ge nanocrystal growth in Ge:SiOx/SiO2 multilayers—a new dc magnetron approach. Nanotechnology 22:485303. doi: 10.1088/0957-4484/22/48/485303 CrossRefGoogle Scholar
  57. Zschintzsch M, von Borany J, Jeutter NM, Mücklich A (2011b) Stacked Ge nanocrystals with ultrathin SiO2 separation layers. Nanotechnology 22:465302. doi: 10.1088/0957-4484/22/46/465302 CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • Ana-Maria Lepadatu
    • 1
    • 2
    • 3
  • Toma Stoica
    • 3
  • Ionel Stavarache
    • 1
  • Valentin Serban Teodorescu
    • 1
  • Dan Buca
    • 3
  • Magdalena Lidia Ciurea
    • 1
    • 4
  1. 1.National Institute of Materials PhysicsMagureleRomania
  2. 2.Faculty of PhysicsUniversity of BucharestMagureleRomania
  3. 3.Peter Grünberg Institute (PGI-9), Forschungszentrum JülichJülichGermany
  4. 4.Academy of Romanian ScientistsBucurestiRomania

Personalised recommendations