“Mr. Mayandi Jeyanthinath & Dr. Richard Feynman”

                                               “There is plenty of room at the bottom”
                                                                                  – Richard Feynman

                                         “There may be plenty of galaxies at the bottom”

                                                                                  – Mayandi Jeyanthinath

 

 

 

               My Supervisors:             

  1. Professor Terje Finstad

    http://www.fys.uio.no/person/info.php?person=210&lang=NO

 

 

 

 

 

 

   2. Professor Andrej Kuznetsov

 

 

 

 

 

 

 

 

   Studies:

 

            Address for correspondence: terje.finstad@fys.uio.no

 

 

           

   Introduction:

 

                        In the search of the galaxies we are in Nanodots (Nano-structures which confine electrons in all three directions are called “quantum dots” (QDs) or “nanodots” (nds/ncs).

            We have certain tasks, which are as follows.

·        Firstly, a detailed study, to optimize the growth conditions of the ncs in order to achieve uniform distribution and appropriate ncs size.

·        Secondly, the optical properties, such as photoluminescence and electroluminescence of the ncs embedded in the SiO2 codoped with Er will be studied. This is to study the 1.54 µm infrared luminescence which is widely used in the optical telecommunication.

·         Finally, the electrical properties of the ncs embedded SiO2 will be analyzed. We will also study the memory effects from the metal insulator semiconductor (MIS) structures based on semiconductor ncs embedded in SiO2.

In the past few decades, there has been considerable interest in semiconductor nanostructures, especially porous Si and Si nanocrystals (ncs) because of their potential applications toward Si-based optoelectronic devices. Due to the novel quantum confinement effect much more interest have been devoted to the growth of Si ncs and fabricated by a variety of techniques such as co-sputtering, chemical vapour deposition, molecular beam epitaxy, gas evaporation, laser ablation, ion implantation and so on.  Ncs have unique electrical, optical, magnetic and thermal properties which are not observed in bulk materials. Uniform and regular arrays of QDs have unusual electrical and optical properties which make them potential candidates for future microelectronic and optoelectronic devices. However, fabrication of these regularly spaced and uniform size quantum dots is a still a challenging issue.

Working towards our task we have currently studied the evolution of Ge, Si ncs in the different structures, and also characterized using AFM, PL (photoluminescence), TEM and FTIR studies. We have done preliminary studies to optimize the growth conditions and we have also obtained interesting results. Here we have introduced some of our new results.  We have also presented some of the results which are yet to be published.

 

 

STUDY 1:

Annett Thøgersen, J. N. Mayandi, Arne Olsen and Terje Finstad, In pursuit of Nanocrystal Quantum Dots of Si in a thin SiO2 layer [Poster]. Scandem2005 23.05.05 - 26.05.05.

 

Structure of study 1:

a) SiO2(~20nm) (sputtered)/ Si-rich SiO2(~8nm)(sputtered)/SiO2 (rto)(~8nm)/Si

b) Si-rich SiO2(~8nm)(sputtered) /SiO2 (rto)(~8nm)/Si

 

In this study we are concentrating to prepare a half-embedded Si ncs templates for the future applications (will be delivered soon). Mostly the electrical and optical properties are dependent on the size, shape and growth mode of the embedded ncs. The challenging issue here is to achieve this special type with a uniform distributed ncs. In our study we are optimizing the  growth parameters for the uniformity.

 

 

 

FIG 1. AFM picture of above structure (a) annealed and etched for 10sec with 1%HF.

 

 
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Further more TEM studies are going on to understand the structural properties and to tune the distribution of ncs. Then we will also investigate the electrical properties of the embedded / half-embedded ncs.

 

 

            STUDY 2:

 

1.       Heng, Chenglin; Finstad, Terje; Li, Yanjun; Mayandi, Jeyanthinath; Jørgensen, Sissel; Storås, Preben; Olsen, Arne; Gunnæs, Anette Eleonora. The precipitation of Ge-rich nano particles in an (Er,Ge) co doped SiO2 matrix . ICMAT 2005; 03.07.2005 - 08.07.2005.

2.       Finstad, Terje; Heng, Chenglin; Li, Yanjun; Mayandi, Jeyanthinath; Olsen, Arne; Jørgensen, Sissel. Strong luminescence from Er in an environment of Ge nanoclusters in SiO2. First International Workshop on Semiconductor Nanocrystals; 10.09.2005 - 12.09.2005

 

Structure of study 2:

a)Ge+SiO2(sputtered)(~ 150nm )/ Ge+Er+SiO2(sputtered)(~50nm)/Ge+SiO2(sputtered)( ~350nm)/ Si

b) SiO2(sputtered)(~ 150nm )/ Er+SiO2(sputtered)(~50nm)/SiO2(sputtered)( ~350nm)/ Si

 

In this work, we have also reported on quite strong 1.54µm photoluminescence (PL) from an (Er, Ge) co-doped SiO2 film deposited by rf magnetron sputtering, similar to the above mentioned structure. The PL intensity reaches a maximum value after the film is annealed at 700 °C for 30 min in N2.

 

From a
 

FIG 1. The ,1.54 µm PL from the above structure (a) after annealed at 500-1100 °C in N2 for 30 min.

 

 
 

From a
 
 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

FIG 3.  FTIR measurements for the above structures, to determine the oxide property, Ge precipitation and Er characteristics.

 

 
 

From b
 
 

 

 


From a
 
 


More details of PL study can be found in: C. L. Heng, T. G. Finstad, P. Storås, Y. J. Li, A. E. Gunnæs and O. Nilsen, Appl. Phys. Lett. 85, 4475 (2004

 

 

 

 

 

 

 

STUDY 3:

1.      Finstad, Terje; Mayandi, Jeyanthinath; Foss, Steinar; Serincan, U.; Turan, Rasit. Luminescence in ion beam synthesized quantum dots correlated with nanocrystal depth and size distrubutions. IMMB2005; 05.09.2005 - 09.09.2005 (submitted)

2.      Mayandi, Jeyanthinath; Finstad, Terje; Foss, Steinar; Serincan, U.; Turan, Rasit. Luminescence from Si nanocrystals in SiO2 films [Poster]. 22nd Nordic Semiconductor Meeting; (submitted)

Structure of study 3:

SiO2(250nm) +Si(implanted)/ Si

 

We have studied the photoluminescence (PL) (Fig.1) from Si nanocrystals embedded in SiO2 and correlate these with the size and distribution of Si nanoclusters. Si nanocrystals in thermal oxide films (~250 nm) where fabricated by 100 keV Si ion implantation at various doses followed by high temperature annealing. After annealing a sample implanted with a dose of 1x1017 cm-2 at 1050 C for two hours a broad photo luminescence peak centered around 880 nm is observed. A dose of 5x1016 cm-2 yields a considerable blue shift of about 100 nm relative to the higher dose as well as a reduction in intensity. Transmission electron microscopy is used to characterize the microstructure of the SiO2 film has also be studied (Fig.2). Finally we show an example of a series of AFM analysis (Fig.3) for different depths in SiO2 film by etching for different times.

 


 

 

 

 

 

 

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


  

                                      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


               

 

 

 

 

 

Electro-luminescence Study: Under investigations……..

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

My Friend:

 

Jan Håvard Bleka

 

 

Co-Advisor:

 

Dr. Heng Chenlin       Chenglin Heng (http://www.fys.uio.no/person/info.php?person=3776&lang=NO)

 

 

 

My senior’s:

1. Mr. Sean Erik Foss

2. Dr. Yiu Yan Kan