An official website of the United States government
We demonstrate the thermo-optic properties of silicon-rich silicon nitride (SRN) films deposited using plasma-enhanced chemical vapor deposition (PECVD). Shifts in the spectral response of Mach-Zehnder interferometers (MZIs) as a function of temperature were used to characterize the thermo-optic coefficients of silicon nitride films with varying silicon contents. A clear relation is demonstrated between the silicon content and the exhibited thermo-optic coefficient in silicon nitride films, with the highest achievable coefficient being as high as (1.65±0.08) ×10−4K-1. Furthermore, we realize an SRN multi-mode interferometer (MMI) based thermo-optic switch with over 20 dB extinction ratio and total power consumption for two-port switching of 50 mW.
more »
« less
Determination of the nonlinear thermo-optic coefficient of silicon nitride and oxide using an effective index method
There is little literature characterizing the temperature-dependent thermo-optic coefficient (TOC) for low pressure chemical vapor deposition (LPCVD) silicon nitride or plasma enhanced chemical vapor deposition (PECVD) silicon dioxide at temperatures above 300 K. In this study, we characterize these material TOC’s from approximately 300-460 K, yielding values of (2.51 ± 0.08) · 10−5K−1for silicon nitride and (5.67 ± 0.53) · 10−6K−1for silicon oxide at room temperature (300 K). We use a simplified experimental setup and apply an analytical technique to account for thermal expansion during the extraction process. We also show that the waveguide geometry and method used to determine the resonant wavelength have a substantial impact on the precision of our results, a fact which can be used to improve the precision of numerous ring resonator index sensing experiments.
more »
« less
- Award ID(s):
- 2023730
- PAR ID:
- 10385367
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 30
- Issue:
- 26
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 46134
- Size(s):
- Article No. 46134
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We present a study of optical bi-stability in a 3.02 refractive index at 1550nm plasma enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) film, as it pertains to bi-stable switching, memory applications, and thermal sensing applications. In this work we utilize an SRN ring resonator device, which we first characterize at low-power and then compare thermo-optic coefficients, (2.12 ± 0.125) × 10−4/°C, obtained from thermal-heating induced resonance shifts to optically induced resonance shifts as well as estimated propagation loss and absorption. We then measure the time response of this nonlinearity demonstrating the relaxation time to be 18.7 us, indicating the mechanism to be thermal in nature. Finally, we demonstrate bi-stable optical switching.more » « less
-
Boron nitride (BN) is a member of Group III nitrides and continues to spark interest among the scientific community for its mechanical properties, chemical inertness, thermal conductivity, and electrical insulating properties. In this study, microwave plasma chemical vapor deposition is used to synthesize BN on silicon substrates. Feed gas mixtures of H2, NH3, and B2H6 are used for a range of systematically varied power, pressure, and flow rate conditions. Plasma optical emission from atomic boron is shown to increase nonlinearly by nearly a factor of five with decreasing chamber pressure in the range from 100 to 10 Torr. Copious amounts of atomic boron in the plasma may be beneficial under some growth conditions for producing high hardness boron-rich nitrides, such as B13N2, B50N2, or B6N, which, to date, have only been synthesized under high pressure/high temperature conditions. Despite the higher atomic boron emission in the plasma at low pressure, BN coatings grown at 15 Torr result in hexagonal BN (B/N ratio of 1), regardless of the B2H6 flow rate used in the range of 0.6–3.0 sccm.more » « less
-
Abstract New deposition techniques for amorphous oxide semiconductors compatible with silicon back end of line manufacturing are needed for 3D monolithic integration of thin‐film electronics. Here, three atomic layer deposition (ALD) processes are compared for the fabrication of amorphous zinc tin oxide (ZTO) channels in bottom‐gate, top‐contact n‐channel transistors. As‐deposited ZTO films, made by ALD at 150–200 °C, exhibit semiconducting, enhancement‐mode behavior with electron mobility as high as 13 cm2V−1s−1, due to a low density of oxygen‐related defects. ZTO deposited at 200 °C using a hybrid thermal‐plasma ALD process with an optimal tin composition of 21%, post‐annealed at 400 °C, shows excellent performance with a record high mobility of 22.1 cm2V–1s–1and a subthreshold slope of 0.29 V dec–1. Increasing the deposition temperature and performing post‐deposition anneals at 300–500 °C lead to an increased density of the X‐ray amorphous ZTO film, improving its electrical properties. By optimizing the ZTO active layer thickness and using a high‐kgate insulator (ALD Al2O3), the transistor switching voltage is lowered, enabling electrical compatibility with silicon integrated circuits. This work opens the possibility of monolithic integration of ALD ZTO‐based thin‐film electronics with silicon integrated circuits or onto large‐area flexible substrates.more » « less
-
Abstract Specific heat measurements from 2 to 300 K of hydrogenated amorphous silicon prepared by hot-wire chemical vapor deposition show a large excess specific heat at low temperature, significantly larger than the Debye specific heat calculated from the measured sound velocity. The as-prepared films have a Schottky anomaly that is associated with metastable hydrogen in the amorphous network, as well as large linear and excess cubic term commonly associated with tunneling two-level systems in amorphous solids. Annealing at 200 °C, a temperature that enables hydrogen mobility but not evaporation, irreversibly reduces the heat capacity, eliminating the Schottky anomaly and leaving a reduced linear heat capacity. A non-monotonic dependence on growth temperature and H content is observed in all effects, except for sound velocity, which suggests that the tunneling two-level systems and the Schottky anomaly are associated with atomic hydrogen and require low density regions to form, while sound velocity is associated with the silicon network and increases with increasing growth temperature.more » « less
