A combined approach to greatly enhancing the photoluminescence of Si nanocrystals embedded in SiO₂

Abstract

An approach combining back- and front-side doping of Ce3+ in Si nanocrystals embedded in SiO2 (nc-Si:SiO2) with hydrogen passivation has been developed, which largely enhances the photoluminescence (PL) of Si nanocrystals. The sample of nc-Si:SiO2 was prepared via a phase separation process of SiO thin film at 1100 °C. For the back-side doping, a SiO2 buffer layer was placed between the CeF3 layer and SiO one, thus Ce3+ doping could be accomplished without disrupting the phase separation of SiO. The front-side doping was then followed by evaporating CeF3 onto the front surface of the formed nc-Si:SiO2, followed by diffusion annealing at 500 °C. The double-side doping enhanced the PL intensity of Si nanocrystals by a factor of 7.3. After hydrogenation of the double-side doped sample, a 14.6-fold increase in the PL intensity was finally achieved.

A combined approach to fabricating Si nanocrystals with high photoluminescence intensity

“…After thermal annealing, the multilayered Si-nc:SiO 2 /SiO 2 sample was prepared. The so-called double-side doping of CeF 3 consists of the backside doping and the front-side one, that is, to dope the formed Si-nc:SiO 2 thin film from both the back and front surface sides, respectively [14]. Since the Si-nc:SiO 2 film cannot be ''peeled'' off the substrate, the backside doping has to be conducted from the very beginning of the sample preparation, as illustrated by Fig.…”

“…Si nanocrystals embedded in SiO 2 matrix, or Si-nc:SiO 2 , has become a promising candidate for this purpose due to its robustness in strength, stability in light emission, and compatibility with the modern Si technology [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In particular, its feature of stimulated emission makes a Si-based laser possible in principle [4,11,12,15].…”

“…However, the relatively low intensity of its photoluminescence (PL) (PL efficiency currently ranges between $1 and 10%) hinders its practical use [5,16]. To enhance the PL intensity of Si nanocrystals, hydrogen passivation of Si-nc:SiO 2 has been used to saturate the dangling bonds as nonradiative centers at the interface between Si and SiO 2 [6,7,14]. This approach normally enhances the PL intensity of Si nanocrystals by a factor of less than 10.…”

“…On the other hand, we noticed that the Si-nc:SiO 2 /SiO 2 multilayered sample [8,9] is much brighter than a single-layered one of Si-nc:SiO 2 for the same amount of excess Si content in addition to its capability of modulating the PL peak position of Si nanocrystals. Recently, a method of CeF 3 doping has been developed, which employs a principle of energy transfer from rare earth ions to Si nanocrystals to enhance the PL intensity of Si nanocrystals [13,14]. This method involves extrinsic factors to enhance the PL emission of Si nanocrystals such as foreign doping ions, which implies that if it is applied to a sample of Si-nc:SiO 2 that already possesses a fairly high PL efficiency, the PL intensity could be further enhanced.…”

Investigation of luminescence from SiC nano-granule films on porous glass substrate

“…Furthermore, the optimal PL performance was obtained when SiC deposited time was 1 h and the glass substrate was etched for 20 min in the annealing sample (450 o C). [2][3][4][5][6][7] , the porous SiC [8,9] , the rare-earth doped SiC [10][11][12] and the SiO 2 -related materials [13] , have been extensively studied. Among them, silicon carbide has attracted special interests because it has potential applications on optoelectronics devices and high-temperature mechanical devices.…”