Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Structure and electrical transport in films of Ge nanoparticles embedded in SiO2 matrix

  • 324 Accesses

  • 22 Citations


The films containing Ge nanoparticles embedded in SiO2 matrix were prepared by RF magnetron sputtering and subsequently by thermal annealing. Their structure was investigated by conventional transmission electron microscopy and high resolution transmission electron microscopy together with energy-dispersive X-ray spectroscopy. The electrical behavior of films was studied by measuring current–temperature and current–voltage characteristics. The structure investigation reveals two kinds of features: a low density of big Ge nanoparticles with sizes from 20 to 50 nm and a network of small amorphous Ge nanoregions/nanoparticles (5 nm size or less) with high density, both being embedded in amorphous SiO2 matrix. The electrical transport was shown to take place through the network of amorphous Ge nanoregions. At low temperature, the T −1/4 dependence of the current was evidenced, while at high temperature, the T −1 Arrhenius dependence was found. At both low and high temperatures, the conductivity is nearly constant. The behavior at low temperature was explained by the hopping mechanism on localized states located in a band near the Fermi energy, while at high temperature by the charge excitation to the extended states.

This is a preview of subscription content, log in to check access.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10


  1. Ahmed AHZ, Tait RN (2003) Characterization of amorphous GexSi1−xOy for micro machined uncooled bolometer applications. J Appl Phys 94:5326–5332. doi:10.1063/1.1609633

  2. Aktağ A, Yilmaz E, Mogaddam NAP, Aygün G, Cantas A, Turan R (2010) Ge nanocrystals embedded in SiO2 in MOS based radiation sensors. Nucl Instr Methods Phys Res B 268:3417–3420. doi:10.1016/j.nimb.2010.09.007

  3. Basa P, Alagoz AS, Lohner T, Kulakci M, Turan R, Nagy K, Horváth ZsJ (2008) Electrical and ellipsometry study of sputtered SiO2 structures with embedded Ge nanocrystals. Appl Surf Sci 254:3626–3629. doi:10.1016/j.apsusc.2007.10.075

  4. Beyer V, von Borany J, Klimenkov M (2007) A transient electrical model of charging for Ge nanocrystal containing gate oxides. J Appl Phys 101:094507. doi:10.1063/1.2723864

  5. Chen WR, Chang TC, Liu PT, Tu CH, Yeh JL, Hsieh YT, Wang RY, Chang CY (2007) Formation of germanium nanocrystals by rapid thermal oxidizing SiGeO layer for nonvolatile memory application. Surf Coat Tech 202:1333–1337. doi:10.1016/j.surfcoat.2007.07.112

  6. Chew HG, Choi WK, Foo YL, Zheng F, Chim WK, Voon ZJ, Seow KC, Fitzgerald EA, Lai DMY (2006) Effect of germanium concentration and oxide diffusion barrier on the formation and distribution of germanium nanocrystals in silicon oxide matrix. Nanotechnology 17:1964–1968. doi:10.1088/0957-4484/17/8/028

  7. 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

  8. Choi WK, Ng V, Ng SP, Thio HH, Shen ZX, Li WS (1999) Raman characterization of germanium nanocrystals in amorphous silicon oxide films synthesized by rapid thermal annealing. J Appl Phys 86:1398–1403. doi:10.1063/1.370901

  9. Choi WK, Ho YW, Ng SP, Ng V (2001) Microstructural and photoluminescence studies of germanium nanocrystals in amorphous silicon oxide films. J Appl Phys 89:2168–2172. doi:10.1063/1.1342026

  10. Choi WK, Chew HG, Hob V, Ng V, Chim WK, Ho YW, Ng SP (2006a) Formation of germanium nanocrystals in thick silicon oxide matrix on silicon substrate under rapid thermal annealing. J Cryst Growth 288:79–83. doi:10.1016/j.jcrysgro.2005.12.033

  11. Choi WK, Chew HG, Zheng F, Chim WK, Foo YL, Fitzgerald EA (2006b) Stress development of germanium nanocrystals in silicon oxide matrix. Appl Phys Lett 89:113126. doi:10.1063/1.2354012

  12. Ciurea ML, Lazanu S, Stavarache I, Lepadatu AM, Iancu V, Mitroi MR, Nigmatullin RR, Baleanu CM (2011) Stress-induced traps in multilayered structures. J Appl Phys 109:013717. doi:10.1063/1.3525582

  13. Coppari F, Chervin JC, Congeduti A, Lazzeri M, Polian A, Principi E, Di Cicco A (2009) Pressure-induced phase transitions in amorphous and metastable crystalline germanium by Raman scattering X-ray spectroscopy, and ab initio calculations. Phys Rev B 80:115213. doi:10.1103/PhysRevB.80.115213

  14. Cosentino S, Liu P, Le ST, Lee S, Paine D, Zaslavsky A, Pacifici D, Mirabella S, Miritello M, Crupi I, Terrasi A (2011a) High-efficiency silicon-compatible photo detectors based on Ge quantum dots. Appl Phys Lett 9:221107. doi:10.1063/1.3597360

  15. Cosentino S, Mirabella S, Miritello M, Nicotra G, Lo Savio R (2011b) The role of the surfaces in the photon absorption in Ge nanoclusters embedded in silica. Nanoscale Res Lett 6:135. doi:10.1186/1556-276X-6-135

  16. Elliott PJ, Yoffe AD, Davis EA (1974) Hopping conduction in amorphous germanium. AIP Conf Proc 20:311–319. doi:10.1063/1.2945979

  17. Fujii M, Inoue Y, Shinji H, Yamamoto K (1996) Hopping conduction in SiO2 films containing C, Si, and Ge clusters. Appl Phys Lett 68:3749–3751. doi:10.1063/1.115994

  18. Fujii M, Mamezaki O, Hayashi S, Yamamoto K (1998) Current transport properties of SiO2 films containing Ge nanocrystals. J Appl Phys 83:1507–1512. doi:10.1063/1.366858

  19. 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

  20. Godet C (2001) Hopping model for charge transport in amorphous carbon. Philos Mag B 81:205–222. doi:10.1080/13642810108216536

  21. Iancu V, Draghici M, Jdira L, Ciurea ML (2004) Conduction mechanisms in silicon-based nano composites. J Optoelectron Adv Mater 6:53–56

  22. Inoue Y, Fujii M, Hayashi S, Yamamoto K (1998) Single electron tunneling through Ge nanocrystal fabricated by cosputtering method. Solid-State Electron 42:1605–1608. doi:10.1016/S0038-1101(98)00079-3

  23. Jensen JS, Leervad Pedersen TP, Pereira R, Chevallier J, Lundsgaard Hansen J, Bech Nielsen B, Nylandsted Larsen A (2006) Ge nanocrystals in magnetron sputtered SiO2. Appl Phys A 83:41–48. doi:10.1007/s00339-005-3479-7

  24. 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

  25. 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

  26. Lepadatu AM, Stavarache I, Stoica TF, Ciurea ML (2011) Study of Ge nanoparticles embedded in an amorphous SiO2 matrix with photoconductive properties. Dig J Nanomater Bios 6:67–73

  27. Li J, Wu XL, Hu DS, Yang YM, Qiu T, Shen JC (2004) Splitting of X-ray diffraction peak in (Ge:SiO2)/SiO2 multi layers. Solid State Commun 131:21–25. doi:10.1016/j.ssc.2004.04.026

  28. Lomas RA, Hampshire MJ, Tomlinson RD, Knott KF (1973) Hall effects and noise measurement in epitaxial, polycrystalline, and amorphous Ge. Phys Stat Sol (a) 16:385–394. doi:10.1002/pssa.2210160206

  29. Maeda Y (1995) Visible photoluminescence from nano crystallite Ge embedded in a glassy SiO2 matrix: evidence in support of the quantum-confinement mechanism. Phys Rev B 51:1658–1670. doi:10.1103/PhysRevB.51.1658

  30. Mott NF (1969) Conduction in non-crystalline materials. III. Localized states in pseudogap and near extremities of conduction and valence bands. Philos Mag 19:835–852. doi:10.1080/14786436908216338

  31. Peibst R, Erenburg M, Bugiel E, Hofmann KR (2010) Effects influencing electron and hole retention times in Ge nanocrystal memory structures operating in the direct tunneling regime. J Appl Phys 108:054316. doi:10.1063/1.3467527

  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

  33. Pollak M, Knotek ML, Kurtzman H, Glick H (1973) DC conductivity of amorphous germanium and the structure of the pseudogap. Phys Rev Lett 30:856–859. doi:10.1103/PhysRevLett.30.856

  34. Ray SK, Das K (2005) Luminescence characteristics of Ge nanocrystals embedded in SiO2 matrix. Opt Mater 27:948–952. doi:10.1016/j.optmat.2004.08.041

  35. Shen JK, Wu XL, Tan C, Yuan RK, Bao XM (2002) Correlation of electroluminescence with Ge nanocrystal sizes in Ge-SiO2 co-sputtered films. Phys Lett A 300:307–310. doi:10.1016/S0375-9601(02)00617-5

  36. Srinivasa Rao N, Pathak AP, Devaraju G, Saikiran V (2011) Growth and characterization of nc-Ge prepared by microwave annealing. Vacuum 85:927–931. doi:10.1016/j.vacuum.2011.01.012

  37. 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

  38. 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

  39. Teodorescu VS, Ciurea ML, Iancu V, Blanchin MG (2008) Morphology of Si nano crystallites embedded in SiO2 matrix. J Mater Res 23:2990–2995. doi:10.1557/jmr.2008.0358

  40. Tzeng SS, Li PW (2008) Enhanced 400–600 nm photo responsivity of metal-oxide-semiconductor diodes with multi-stack germanium quantum dots. Nanotechnology 19(235203):1–6. doi:10.1088/0957-4484/19/23/235203

  41. 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

  42. Zhang B, Shrestha S, Green MA, Conibeer G (2010b) Surface states induced high P-type conductivity in nano structured thin film composed of Ge nanocrystals in SiO2 matrix. Appl Phys Lett 97:132109. doi:10.1063/1.3496031

  43. 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

  44. Zhao J, Rebohle L, Gebel T, von Borany J, Skorupa W (2002) Bulk-limited conduction of Ge-implanted thermally grown SiO2 layers. Solid-State Electron 46:661–664. doi:10.1016/S0038-1101(01)00322-7

  45. Zhen C, Liu Y, Ma L, Pang Z, Pan C, Hou D (2010) Ferromagnetism in Ge/SiO2 multilayer films. J Appl Phys 107:043901. doi:10.1063/1.3294621

  46. Zheng F, Choi WK, Lin F, Tripathy S, Zhang JX (2008) Stress tuning of Ge nanocrystals embedded in dielectrics. J Phys Chem C 112:9223–9228. doi:10.1021/jp801529j

Download references


This work was supported from Project No. 471/2009 (ID 918/2008), Ideas Program, National Research, Development and Innovation Plan 2007–2013.

Author information

Correspondence to Magdalena Lidia Ciurea.

Additional information

All the authors contributed equally to this article.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Stavarache, I., Lepadatu, A., Maraloiu, A.V. et al. Structure and electrical transport in films of Ge nanoparticles embedded in SiO2 matrix. J Nanopart Res 14, 930 (2012).

Download citation


  • Nanoparticles
  • Magnetron sputtering
  • TEM
  • Electron irradiation
  • Conduction mechanisms
  • Nanostructures