Dopants and defects in diamond

Controlling the charge state of single nitrogen-vacancy centers in diamond

Nitrogen-vacancy defects (NV) in the diamond lattice have been extensively studied in the past since they can act as single photon emitters in the visible range with absolute photo stability. Due to the possibility to prepare and readout their corresponding spin state optically and because of extraordinary long spin coherence times (T2=1.8ms @RT) they have found applications in novel fields like quantum computation and single spin magnetometry. In this context, our research group is investigating the effect of diamond surface termination on the charge state of NV centers in diamond. Furthermore, we are working on finding ways to gain electrostatic control over the charge of single NV centers.

We have recently shown that the fluorescence of NV centers in the vicinity of the diamond surface can be suppressed depending on the surface termination. Compared to an oxygen-terminated surface, no fluorescence is observed from NV in the vicinity of hydrogen-terminated surfaces. This effect is due to the surface band bending  related to the two-dimensional hole gas induced at hydrogen-terminated diamond surfaces. Thus, shallowly implanted NV centers will thus be rendered either neutrally or even positively charged. Being positively charged, the NV center loses its fluorescent properties.
Using the surface-conductivity of a hydrogen-terminated diamond surface in air, we are working on achieving electrostatic control of the charge state of single NV centers in diamond with an external gate electrode.

Diamond-based photodetectors

Hydrogenated diamond exhibits a p-type surface conductivity in air. Patterning a thin oxidized line into hydrogenated areas of a diamond surface results in an effective lateral energy barrier for the two-dimensional hole gas. We investigate the sub-bandgap optoelectronic phenomena induced by such a barrier structure at room temperature.
A photoconductive gain of the hole conductivity across the barrier is observed when illuminating the oxidized line. This effect is explained by the influence of photogenerated electrons trapped in defect states located within the oxidized line. The trapped electrons affect the electrostatic potential landscape of the circuit such that they lower the energy barrier for the hole gas. In turn, an increased optically induced conductance is measured. We have shown that the designed structures can operate as photodetectors in the ultra-violet range. Results on our thinnest oxygen lines suggest that the spatial resolution of such a photodetector can be as good as 70 nm or even below.

 

People on the project:

Moritz Hauf, Max Seifert, Wojciech Gajewski

 

Selected publications:

  • Chemical control of the charge state of nitrogen-vacancy centers in diamond
    M. V. Hauf, B. Grotz, B. Naydenov, M. Dankerl, S. Pezzagna, J. Meijer, F. Jelezko, J. Wrachtrup, M. Stutzmann, F. Reinhard, and J. A. Garrido
    Physical Review B - Rapid Communications 83, 081304(R) (2011)
    Download
  • Photoconductance of a submicron oxidized line in surface conductive single crystalline diamond
    M. Stallhofer, M. Seifert, M. Hauf, G. Abstreiter, M. Stutzmann, J. A. Garrido, A. Holleitner
    Appl. Phys. Lett. 97, 111107 (2010)
    Download

 

Cooperations:

J. Wrachtrup, University of Stuttgart

A. Holleitner, ZNN, Technische Universität München

 

Funding:

Nanosystems Initiative Munich (NIM),
Graduate School for Complex Interfaces (CompInt)

TUM Technische Universität München TUM Technische Universität München Physik Department Elektrotechnik und Informationstechnik TUM Technische Universität München
 

Upcoming Events

3.06.2013  
Benno Blaschke
Graphene SGFETs for biosensing applications

poster, Graphene Week 2013, Chemnitz, Germany

 

6.06.2013  
Jose A. Garrido
Graphene sensors for bioelectronic applications

plenary talk, Graphene Week 2013, Chemnitz, Germany

 

3.09.2013  
Roberta Caterino 
Novel functionalization of diamond surfaces for protein-based hybrid systems

talk, International Conference on Diamond and Carbons Materials, Riva del Garda, Italy

 

5.09.2013 
Roberta Caterino
Bio-photovoltaics based on hybrid systems of reaction centers and diamond

talk, International Conference on Diamond and Carbons Materials, Riva del Garda, Italy