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1. Introducing gallium in silicon and thin film polysilicon using self assembled monolayer doping

   https://doi.org/https://doi.org/10.1016/j.matlet.2022.132839  

   Carolyn Spaulding; Alex Taylor; Scott Williams; Glenn Packard; Gabriel Curvacho; Santosh Kurinec (October 2022, Materials letters)

   Aldo R. Boccaccini (Ed.)

   Monolayer Doping (MLD) is a technique involving the fmmation of a self-assembled dopant-containing layer on the substrate. The dopant is subsequently incorporated into the substrate by annealing, fmming a diffused region. Following MLD, samples were capped with silicon dioxide and rapid the1mal annealed (RTA). In this work, gallium doping using MLD has been demonstrated. Gallium containing compound Tris (2,4 pentanedionato) gallium(III) was synthesized, and shown to be suitable for monolayer doping silicon subsa-ates and deposited thin film polysi!icon. Seconda1y ion mass spectroscopy (SIMS) and spreading resistance probe (SRP) measurements were performed to determine the dopant profiles and dopant elecu-ical activation. TI1ese results showed that a dose of l.6*1015 atoms/cm2 was received, and the gallium dopant produced a 0.2 µm junction in 11-type silicon. For polysilicon, tlle entire 0.4 µm film was evenly doped, witll a concenu-ation greater than 1019 atoms/cm3 tllroughout. 

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2. Thermal hysteresis phenomena in aqueous xanthan gum solutions

   https://doi.org/10.1016/j.foodhyd.2023.108973  

   Nsengiyumva, Emmanuel M.; Heitz, Mark P.; Alexandridis, Paschalis (November 2023, Food Hydrocolloids)

   The anionic hydrocolloid polysaccharide xanthan gum is widely used in the food and petroleum industries (among others) as a viscosity enhancement polymer due to its high viscosity at low concentrations and moderate temperatures. The physical properties of microbial polysaccharide xanthan gum aqueous solutions were investigated using temperature dependent viscosity measurements. Specifically, the effect of thermal history on the solution viscosity was investigated. Heating and cooling cycles were assessed in two ways, by using a “sawtooth” and “triangle” pattern, which essentially differed in the rates of cooling. The sawtooth method used a cooling rate of 2.0 ◦C min􀀀 1 whereas the triangle pattern had a cooling rate of 0.20 ◦C min􀀀 1. The sawtooth cooling rate was controlled by the speed at which the Peltier device could cool the sample, and the triangle rate was governed by the time required to measure the viscosity at each temperature on return to the initial value. Cycles measured using the sawtooth pattern for 16 mg/kg xanthan gum in water showed an 8–10% overall decrease in the viscosity over four complete cycles. Comparatively, at 320 mg/kg the xanthan gum solution showed a 25% decrease in viscosity over four cycles. The observed temperature dependent viscosity variation suggested minor modifications in the physical network structure of xanthan gum. When using a triangle heating/cooling pattern, the overall decrease in the xanthan gum solution viscosity was 5–7% for 16 mg/kg and only 10% change for 320 mg/ kg solutions. The activation energy of viscous flow for the aqueous xanthan gum solutions by either method was ~15.0 kJ/mol under all conditions. The data showed that temperature and heating cycles influence xanthan gum viscosity and thermal history, which depends more strongly on xanthan gum concentration than solution temperature. 

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3. Large remnant polarization and great reliability characteristics in W/HZO/W ferroelectric capacitors

   https://doi.org/10.3389/fmats.2022.969188  

   Asapu, Shiva; Pagaduan, James Nicolas; Zhuo, Ye; Moon, Taehwan; Midya, Rivu; Gao, Dawei; Lee, Jungmin; Wu, Qing; Barnell, Mark; Ganguli, Sabyasachi; et al (August 2022, Frontiers in Materials)

   In this work, the effect of rapid thermal annealing (RTA) temperature on the ferroelectric polarization in zirconium-doped hafnium oxide (HZO) was studied. To maximize remnant polarization (2P r ), in-plane tensile stress was induced by tungsten electrodes under optimal RTA temperatures. We observed an increase in 2P r with RTA temperature, likely due to an increased proportion of the polar ferroelectric phase in HZO. The HZO capacitors annealed at 400°C did not exhibit any ferroelectric behavior, whereas the HZO capacitors annealed at 800°C became highly leaky and shorted for voltages above 1 V. On the other hand, annealing at 700 °C produced HZO capacitors with a record-high 2P r of ∼ 64 μ C cm −2  at a relatively high frequency of 111 kHz. These ferroelectric capacitors have also demonstrated impressive endurance and retention characteristics, which will greatly benefit neuromorphic computing applications. 

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4. Microscale Engineering of n-Type Doping in Nanostructured Gallium Antimonide: AC Impedance Spectroscopy Insights on Grain Boundary Characterization and Strategies for Controlled Dopant Distribution

   https://doi.org/10.3390/mi14091801  

   Hall, Michael J; Vashaee, Daryoosh (September 2023, Micromachines)

   This paper investigates the microscale engineering aspects of n-type doped GaSb to address the challenges associated with achieving high electrical conductivity and precise dopant distribution in this semiconductor material. AC impedance spectroscopy is employed as a reliable technique to characterize the microstructural and electrical properties of GaSb, providing valuable insights into the impact of grain boundaries on overall electrical performance. The uneven distribution of dopants, caused by diffusion, and the incomplete activation of introduced dopants pose significant obstacles in achieving consistent material properties. To overcome these challenges, a careful selection of alloying elements, such as bismuth, is explored to suppress the formation of native acceptor defects and modulate band structures, thereby influencing the doping and compensator formation processes. Additionally, the paper examines the effect of microwave annealing as a potential solution for enhancing dopant activation, minimizing diffusion, and reducing precipitate formation. Microwave annealing shows promise due to its rapid heating and shorter processing times, making it a viable alternative to traditional annealing methods. The study underscores the need for a stable grain boundary passivation strategy to achieve significant improvements in GaSb material performance. Simple grain size reduction strategies alone do not result in better thermoelectric performance, for example, and increasing the grain boundary area per unit volume exacerbates the issue of free carrier compensation. These findings highlight the complexity of achieving optimal doping in GaSb materials and the importance of innovative analytical techniques and controlled doping processes. The comprehensive exploration of n-type doped GaSb presented in this research provides valuable insights for future advancements in the synthesis and optimization of high-conductivity nanostructured n-type GaSb, with potential applications in thermoelectric devices and other electronic systems. 

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5. Influence of Controlled Cooling Rates During Thermal Processing of Ti 6% Al 4% V Alloys Using In-Situ Scanning Electron Microscopy

   https://doi.org/10.1557/adv.2020.190  

   Kane, Genevieve A; Frey, M. David; Hull, Robert (January 2020, MRS Advances)

   ABSTRACT We describe experimental approaches to real time examination of the microstructural evolution of Ti 6%Al 4%V upon cooling from above the beta transus (~995 °C) while imaging in the scanning electron microscope. Ti 6%Al 4%V is a two phase, α+β titanium alloy with high strength and corrosion resistance. The β →α transformation on cooling can give rise to different microstructures and properties through various thermal treatments. Fully lamellar microstructures, bi-modal microstructures, and equiaxed microstructures can each be obtained by accessing different cooling rates upon the final treatment above the beta temperature, each resulting in uniquely enhanced material properties. Utilizing the capabilities of a heating/ tensile stage developed by Kammrath & Weiss Inc., are able to apply real-time imaging techniques in the scanning electron microscope to monitor the development of the microstructure. Annealing temperatures up to 1100 °C are attainable, with cooling rates ranging from 0.1 ° C per second to 3.3 °C per second. This has allowed us to directly observe the formation of lamellae at different annealing temperature/ cooling rate combinations to determine the lamellar microstructure width, separation, and colony size. 

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