Kemal Rüzgar Akın Bacıoğlu Hacettepe University, Physics Engineering Dept.,AYIL, Beytepe, 06800, Ankara, Turkey. HACETTEPE UNIVERSITY Producing Nanocrystalline Silicon Suboxide Thin Films nc-SiOx:H (x<1) in PECVD MOTIVATION: Silicon nanocrystals (nc-Si) in an amorphous silicon oxide a-SiOx:H matrix, has generated significant interest in the nc-Si/a-SiOx:H system because of its potential applications in electronics, optoelectronics, and optical devices in Si-compatible technologies. At present, however, many fundamental aspects of the synthesis and structure of nc-Si in a-SiOx:H are still uncertain, despite significant efforts over recent years. SAMPLE PRODUCTION: Samples were deposited in a single chamber RF-PECVD system with particular conditions. nc-SiOx:H thin film samples were deposited by using CO2 and SiH4 gas mixture diluted by H2, at different CO2 and H2 flow rates. The flow ratio of CO2( ) and dilution ratio of H2 ( were varied from 0 to 85% and from 90 to 95%, respectively. The other parameters kept constant during process were as following, chamber pressure of 1.9 Torr, 13.56 MHz RF power density of 60 mW/cm 2 and substrate temperature of 150C. INTRODUCTION MEASUREMENT RAMAN SCATTERING FT-IR MEASUREMENTS RESULTS AND DISCUSSIONS RESULTS: • Raman scatterring measurements show that crystallization was obtained with H2 dilution of CO2 and SiH4 mixture. • Oxygen concentration directly affects the crystallization ratio. • FT-IR measurements prove that CO2 and H2 flow rates govern H and O content of the samples. • Temperature dependent dark conductivity measurements reveal the effect of nano-crystallization on activation energy. • Optical band gap results vary with dilution rates and gives clues about the effect of crystallization on band gap. REFERENCES: [1] Decai Yu, Sangheon Lee, and Gyeong S. Hwang, Journal of applied physics 102, 084309 (2007) [2] Blakemore J.S., 1974, Solid State Physics 2nd, W.B. Saunders Company. [3] Swanepoel R., 1983, Determination of the Thickness and Optical Constant of Amorphous Silicon, J. Phys. E: Sci. Instrum., 16, 1214. [4] Pankove J. I., 1975, Optical Processes in Semiconductors, Dover Publication, New York, 422. [5] G. Lucovsky, J. Yang, S. S. Chao, J. E. Tyler and W. Czubatyj, Phys. Rev. B 28(6), 3225 (1983). [6] Rath J.K., Klerk L.A., Gordijn A., Schropp R.E.I., 2006, Mechanism of Hydrogen Interaction with the Growing Slicon Film, 90,3385-3393. [7] Iqbal Z., Webb a.P. and Veprek S., 1980, Polycrystalline Silicon Films Deposited in a Glow Discharge at Temperatures Below 250ºC, App. Phys. Lett., 36 (2), 163-165. 0 10 20 30 40 50 60 70 80 90 100 0 1 2 3 4 5 6 7 8 9 r[H]=%99±5 r[H]=%95±5 r[H]=%95±5 r[H]=%90±5 [O] (at. %) r[CO 2 ] (%) Power:60±5mW/cm 2 Pressure:1.9Torr Temperature:150±5 0 C 100 200 300 400 500 600 200 300 400 500 600 700 800 900 1000 1100 1200 Intensity (arb. units) Raman Shift (cm -1 ) OPTOELECTRONIC MEASUREMENTS 1 2 3 4 5 6 2080 2090 2100 2110 2120 k peak (cm -1 ) [H] (at. %) Power:60±5mW/cm 2 Pressure:1.9 Torr Temperature: 150±5 0 C Each data have different oxygen concentration 0 1 2 3 4 5 6 7 8 9 10 11 12 0 10 20 30 40 50 60 70 80 r[H]=%99±5 r[H]=%95±5 r[H]=%95±5 r[H]=%90±5 X c (%) [O] (at. %) Power:60±5mW/cm 2 Pressure:1.9 Torr Temperature: 150±5 0 C x u Sample Name r(CO 2 ) (%) r(H 2 ) (%) X c (%) Optical E g (eV) K6 50±8 99±1 1.2±1 2.19±0.1 K11 83±3 99±1 9±0.5 2.11±0.1 K15 66±5 95±2 19±0.5 2.05±0.1 K26 33±3 90±3 50±4 1.94±0.07 K21 44±2 95±2 60±10 1.83±0.05 THE SYSTEM AND TECHNIQUES USED • PECVD SYSTEM • FT-IR SPECTROSCOPY • RAMAN SPECTROSCOPY • CPM EXPERIMENT SETUP • TRANSMİSSİON EX. SETUP : crystalline peak 1 related with crystalline silisium : crystalline peak 2 related with crystalline silisium : amorphous peak related with amorphous silisium c m a I I I c m c c m a I I X I I I     CRYSTALLINE RATIO CALCULATIONS CONCENTRATION CALCULATIONS 1 1 ~1000 1 ~2100 1 [ ] at. % () 0,156% . [ ] at. % () 0,77% . cm cm O A k dk A eV cm H B k dk B eV cm               DISCUSSION: Results show that different dilution rates of CO2 and H2, with proved concentration by FT-IR spectroscopy, affect the crystallization ratio which changes the structure, optical and electrical properties of the samples. Crystalline ratio is basically in relation with electrical properties of nc-SiOx:H sample. Optical properties of nc-SiOx:H, especially optical gap, are not so much different than conventional a- SiOx:H samples which forms the hosting structure in nc-SiOx:H. Its main reason is the dominance of a-SiOx:H. The existence of nc-Si grains results a decreasing effect on band gap while dominant character of thin films is amorphous like structure . For understanding quantum size effect in matrix, samples should have more nc-Si grains that distrubuted all matrix. PERSONAL INFO: PHONE: (0312) 2976762 ADRESS: Hacettepe University, Physics Engineering Dept.,AYIL, Beytepe, 06800, Ankara, Turkey. E-MAİL 1: kruzgar@hacettepe.edu.tr E-MAİL 2: k.ruzgar01@gmail.com 100 150 200 250 300 350 400 450 500 550 600 650 200 400 600 800 1000 1200 1400 1600 Intensity (arb. units) Raman Shift (cm -1 ) r[O]=%17±5 r[O]=%30±5 r[O]=%38±5 r[O]=%45±5 Power:60±5mW/cm 2 Pressure:1.9 Torr Temperature: 150±5 0 C 0 1 2 3 4 5 6 0 10 20 30 40 50 60 70 80 o o d[H]=%95±5 d[H]=%95±5 r[H]=%90±5 X c (%) [H] (at. %) Power:20±5mW/cm 2 Pressure:1.9 Torr Temperature: 150±5 0 C o 0 800 900 1000 1100 1200 1300 0,40 0,45 0,50 0,55 0,60 0,65 0,70 0,75 0,80 Absorbance (arb. units) k(cm -1 ) r[CO2]=%0 r[CO2]=%50±5 r[CO2]=%66±5 r[CO2]=%75±5 r[CO2]=%80±5 r[CO2]=%83±5 0 20 40 60 80 100 0,8 0,9 1,0 1,1 1,2 1,3 o r[H]=99±5 r[H]=95±5 r[H]=95±5 r[H]=90±5 E A (eV) X c (%) Power: 60±5mW/cm 2 Pressure: 1.9 Torr Temperature:150±5 0 C o 2 2 2 4 [ ( )] co co co SiH r f f f   2 2 2 4 [ ( )] H H H SiH r f f f   0 2 4 6 8 10 12 980 990 1000 1010 1020 1030 1040 1050 1060 1070 r[H]=%99±5 r[H]=%95±5 r[H]=%95±5 r[H]=%90±5 k peak (cm -1 ) [O] (at. %) Power:60±5mW/cm 2 Pressure:1.9Torr Temperature:150±5 0 C ACTIVATION ENERGY CALCULATION 0 ( ) energy A E kT d A I T Ie E activation    1 ( ) ~1000 ~2100 bonding type k cm Si O Si Si H     1,4 1,6 1,8 2,0 2,2 2,4 100 1000 10000 r[O]=%50±5 r[O]=%44±5 r[O]=%38±5 r[O]=%33±5 r[O]=%29±5 r[O]=%16±5 r[O]=%10±5 Arbsorption Coefficient (arb. units) h (eV) Power: 60±5mW/cm 2 Pressure: 1.9 Torr Temperature:150±5 0 C