No abstract

Chalcogenide phase change materials (PCMs), featuring a large contrast in optical properties between their non-volatile amorphous and crystalline states, have triggered a surge of interest for their applications in ultra-compact photonic integrated circuits with long-term near-zero power consumption. Over the past decade, however, PCM-integrated photonic devices and networks suffered from the huge optical loss of various commonly-used PCMs themselves. In this paper, we focused on the deposition, characterization, and monolithic integration of an emerging low-loss phase change material, Sb2Se3 on a silicon photonic platform. The refractive index contrast between the amorphous and crystalline phase of the evaporated Sb-Se thin film was optimized up to 0.823 while the extinction coefficient remains less than 10−5 measured by ellipsometry. When integrated on a silicon waveguide, the propagation loss introduced by the amorphous thin film is negligibly low. After crystallization, the propagation loss of a magnetron-sputtered Sb-Se patch-covered silicon waveguide is as low as 0.019 dB/µm, while its thermal-evaporated counterpart is below 0.036 dB/µm.

A theoretical study of the electronic structure and spectroscopic properties of the low-lying electronic states of the molecule SiBThe properties of and potential uses for thin films of amorphous Si:B alloys are summarized. The films were deposited by low-pressure chemical vapor deposition of silane and dihorane. The boron content of the samples was controlled by regulating the reaction of diborane and silane gases during the deposition. The alloy and its oxides possess many desirable properties for microelectronic applications, including high microhardness, resistance to chemical etching, high and tailorable conductivity, ease of oxidation, and (for the oxide) high resistivity and dielectric strength. The microstructural stability of the films is excellent. The volume fraction of crystallinity of the as-deposited films was reduced dramatically by increasing the boron content, as was crystallization upon annealing. Transport at low temperatures is seen to be dominated by hopping. The linear oxidation rate was observed to be radically enhanced by the presence of large amounts of boron. The electrical properties of the oxides were seen to be comparable to Si0 2 . Using a simple model relating the physical mode of boron incorporation in the amorphous network, mechanisms for the crystallization inhibition, the oxidation enhancement, and the electrical properties are discussed. These are consistent with stoichiometric and spectroscopic properties of the alloy and its oxides.

Laser pulses can be utilized to induce intermediate states of phase change materials between amorphous and crystalline phases, making phase change materials attractive and applicable for multi-level storage applications. In this paper, intermediate states of Ge2Sb2Te5 thin films induced via employing a nanosecond multi-pulse laser with different energy and pulse duration were performed by Raman spectroscopy, reflection measurement and thermal simulations. Upon laser-crystallized Ge2Sb2Te5 films, optical functions change drastically, leading to distinguishable reflectivity contrasts of intermediate states between amorphous and crystalline phases due to different crystallinity. The changes in optical intensity for laser-crystallized Ge2Sb2Te5 are also accompanied by micro-structure evolution, since high-energy and longer pulses result in higher-level intermediate states (corresponding to high reflection intensity) and largely contribute to the formation of stronger Raman peaks. By employing thermal analysis, we further demonstrated that the variations of both laser fluence and pulse duration play decisive roles in the degree of crystallinity of Ge2Sb2Te5 films. Laser fluence is mainly responsible for the variations in crystallization temperature, while the varying pulse duration has a great impact on the crystallization time. The present study offers a deeper understanding of the crystallization characteristic of phase change material Ge2Sb2Te5.

No abstract