The Influence of Carbon on the Structure and Photoluminescence of Amorphous Silicon Carbonitride Thin Films

Abstract

Current microelectronic devices and integrated optoelectronics are strongly dominated by the silicon technology. Despite being the fundamental material in a wide range of device applications, the indirect band gap nature of silicon causes difficulties in the creation of visible luminescence from silicon based devices. Quantum confinement effects confirm the formation of silicon nanoclusters in the dielectric matrices resulting in efficient luminescence at room temperature. Among several candidates for the host matrix of silicon based materials, silicon carbonitride (SiCN) is a less studied structure exhibiting interesting features due to the combination of unique characteristics of silicon carbide and silicon nitride compounds.In this contribution, we have investigated the effect of the carbon fraction influencing the optical and structural properties of the SiCN matrix. To achieve this aim SiCN thin films have been fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) using 30% SiH 4 in Ar, 10% N 2 in Ar, and pure CH 4 as the gas sources. In addition, for comparison, a set of silicon nitride and silicon carbide samples were fabricated as well. Following their deposition, all films were subjected to thermal annealing in a quartz tube furnace under flowing gases N 2 and N 2 + 5% H 2 for one hour at a wide range of temperatures up to 1200 °C.The compositions of the films were determined through Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) for samples deposited on both crystalline silicon and glassy carbon substrates. For the photoluminescence (PL) emission at room temperature, a 17 mW 325 nm HeCd laser was employed as the excitation source. Combinations of advanced techniques (Fourier transform infrared spectroscopy, Xray photoelectron spectroscopy, and high resolution transmission electron microscopy) were employed to acquire insight into the correlation between the luminescent properties and the structure of amorphous silicon carbonitride. X-ray absorption spectroscopy (XAS) has been carried out at the Si L3,2-edge on the high resolution variable line spacing plane grating monochromator (VLS PGM) 11ID-2 beamline at the Canadian Light Source synchrotron facility to obtain detailed information of silicon nanoclusters affecting the visible emission.The RBS spectra of samples deposited on glassy carbon substrates gave well separated carbon and nitrogen peaks of sample compositions varying from stoichiometric silicon nitride to the high carbon content silicon carbonitirde. PL results indicated a significant enhancement in the visible luminescence occurring at lower annealing temperatures and longer wavelengths in more carbon-rich films up to a certain ratio of CH 4 /N 2 . By continuing to increase the carbon content in the SiCN matrix both the PL emission intensity and features related to Si-C bond started to increase. X-ray absorption spectra of several annealed SiCN thin films at the Si L3,2-edge indicated that the Si-N peak decreased and ...

Influence of Deposition Conditions on the Characteristics of Luminescent Silicon Carbonitride Thin Films

“…The room-temperature PL spectra of the samples were measured in a wavelength range extending from the region of the near-infrared (NIR) (1100 nm) to the UV (350 nm) using charge-coupled device (CCD) arrays and a 325 nm He-Cd laser (E exc = 3.82 eV) with an optical power of 5 mW exciting an area of 2.3 mm 2 . More details regarding the spectrometer and system response used for the correction can be found in Reference 28.…”

“…2 This is a consequence of their unique properties inherited from the combined properties of binary substructures, silicon carbide (SiC), silicon nitride (SiN), and carbonitride (CN). On the one hand, the durability and hardness of SiN structures cannot compete with those of carbon-based hard counterparts such as diamond-like carbon (DLC), CN, and SiC materials.…”

“…We previously showed that the visible photoluminescence (PL) emission from SiC x N y films is stronger than that of SiC and SiN 3 materials and all optical properties (bandgap, transmittance, index of refraction, and light emission) can be controlled by adjusting the film compsoition. 2,17 Despite the advantages of SiC x N y films concerning both mechanical and optical properties, the study of this complex structure is not straightforward due to the presence of three elements (carbon, nitrogen, and silicon). Moreover, depending on the fabrication technique, a quaternary structure containing hydrogen may be produced.…”

XANES and XES Studies of Luminescent Silicon Carbonitride Thin Films

“…(a), undoped sample exhibits a very broad PL spectrum covering the visible spectral range from 400 to 750 nm. More details of the PL properties of different compositions of silicon carbonitride samples with varying carbon content have been previously discussed (13). As the annealing temperature was increased, the maxima of the PL spectrum red-shifted and the intensity of the main emission peak reached a maximum following 500°C annealing.…”

Structural and Optical Properties of Luminescent Silicon Carbonitride Thin Films

“…One of the superior features of SiCN-based matrix is the broad range of stoichiometries that can be adjusted by the experimental deposition conditions (4). In our previous work, several techniques were applied to obtain detailed information on these a-SiCN:H thin films grown using either inductively coupled plasma chemical vapour deposition (ICP PECVD) or electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR PECVD) techniques (5,6). In addition, the incorporation of rare earth elements into silicon-based materials appeared to enhance greatly the photoluminescence (PL) emission.…”