Browsing by Author "Leong, Keith R."

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Erbium-Doped Amorphous Carbon-Based Thin Films: A Photonic Material Prepared by Low-Temperature RF-PEMOCVD
(2014-03-01)
Hsu, Hui-Lin
;
Leong, Keith R.
;
Teng, I-Ju
;
Halamicek, Michael
;
Juang, Jenh-Yih
The integration of photonic materials into CMOS processing involves the use of new materials. A simple one-step metal-organic radio frequency plasma enhanced chemical vapor deposition system (RF-PEMOCVD) was deployed to grow erbium-doped amorphous carbon thin films (a-C:(Er)) on Si substrates at low temperatures (<200 degrees C). A partially fluorinated metal-organic compound, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) Erbium(+III) or abbreviated Er(fod)(3), was incorporated in situ into a-C based host. Six-fold enhancement of Er room-temperature photoluminescence at 1.54 mu m was demonstrated by deuteration of the a-C host. Furthermore, the effect of RF power and substrate temperature on the photoluminescence of a-C:D(Er) films was investigated and analyzed in terms of the film structure. Photoluminescence signal increases with increasing RF power, which is the result of an increase in [O]/[Er] ratio and the respective erbium-oxygen coordination number. Moreover, photoluminescence intensity decreases with increasing substrate temperature, which is attributed to an increased desorption rate or a lower sticking coefficient of the fluorinated fragments during film growth and hence [Er] decreases. In addition, it is observed that Er concentration quenching begins at similar to 2.2 at% and continues to increase until 5.5 at% in the studied a-C: D(Er) matrix. This technique provides the capability of doping Er in a vertically uniform profile.
In-situ doping of erbium in hydrogenated amorphous carbon by low temperature metalorganic radio frequency plasma enhanced chemical vapor deposition
(2014-11-03)
Hsu, Hui-Lin
;
Leong, Keith R.
;
Halamicek, Michael
;
Teng, I-Ju
;
Mahtani, Pratish
A significant improvement in the photoluminescence of erbium doped amorphous carbon (a-C: H(Er)) is reported. The effects of the RF power on the anode and cathode a-C: H films were investigated in terms of the microstructural and local bonding features. It was determined that Er doped a-C: H films should be placed on the anode to obtain wider bandgap and lower percentage of sp(2) carbon bonding. The metalorganic compound, tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) Erbium(+III) or Er(fod)(3), was incorporated in-situ into an a-C: H host by metalorganic rf plasma enhanced chemical vapor deposition. This technique provides the capability of doping Er in a vertically uniform profile. The high erbium concentration (3.9 at.%), partial fluorination of the surrounding ligands, and the large optical bandgap of the host a-C: H are the primary factors that enable enhancement of the photoluminescence. (C) 2014 Elsevier B. V. All rights reserved.
Reduction of Photoluminescence Quenching by Deuteration of Ytterbium-Doped Amorphous Carbon-Based Photonic Materials
(2014-08-01)
Hsu, Hui-Lin
;
Leong, Keith R.
;
Teng, I-Ju
;
Halamicek, Michael
;
Juang, Jenh-Yih
In situ Yb-doped amorphous carbon thin films were grown on Si substrates at low temperatures (<200 degrees C) by a simple one-step RF-PEMOCVD system as a potential photonic material for direct integration with Si CMOS back end-of-line processing. Room temperature photoluminescence around 1 mu m was observed via direct incorporation of optically active Yb3+ ions from the selected Yb(fod)(3) metal-organic compound. The partially fluorinated Yb(fod)(3) compound assists the suppression of photoluminescence quenching by substitution of C-H with C-F bonds. A four-fold enhancement of Yb photoluminescence was demonstrated via deuteration of the a-C host. The substrate temperature greatly influences the relative deposition rate of the plasma dissociated metal-organic species, and hence the concentration of the various elements. Yb and F incorporation are promoted at lower substrate temperatures, and suppressed at higher substrate temperatures. O concentration is slightly elevated at higher substrate temperatures. Photoluminescence was limited by the concentration of Yb within the film, the concentration of Yb ions in the +3 state, and the relative amount of quenching due to the various de-excitation pathways associated with the vibrational modes of the host a-C network. The observed wide full-width-at-half-maximum photoluminescence signal is a result of the variety of local bonding environments due to the a-C matrix, and the bonding of the Yb3+ ions to O and/or F ions as observed in the X-ray photoelectron spectroscopy analyses.