Integrated Calendar

https://weizmann.zoom.us/j/99592122461?pwd=MjM4ZDN0ZDFVeGZOYkdqQi9CUy9uUT09


Semiconductor nanowires (NWs) are quasi 1D nanostructures, exhibiting distinctive physical properties suitable for efficient bottom-up design of nanodevices. A challenging limiting step of their integration into planar functional systems is the difficulty to align them on horizontal surfaces. One simple and elegant way to avoid post growth assembly of NWs is to grow them horizontally in the first place. Over the past decade, our group has established the surface guided growth of horizontal semiconductor NWs aligned by crystalline substrates with controlled crystallographic orientations, directions and position. As the NWs are comprised of different semiconductors, they are optically active is different spectral regimes including the UV and visible range. However, optical activity in the pivotal infrared (IR) regime is not yet exhibited for guided NWs and a systematic exploration of it can pave the way for effective devices for telecommunication and night vision technologies. CdTe, a narrow band-gap II-VI semiconductor (~1.5 eV), is an attractive candidate owing to its promising optical and electrical properties, making it an attractive material for solar cells and near IR (NIR) photodetectors. Its alloys with mercury, known as MCT (HgxCd1-xTe) are already central components of efficient IR photodetectors due to continuous bandgap narrowing with growing percentage of mercury.
In this work, we present the vapor-liquid-solid (VLS) growth and self-alignment of surface guided CdTe NWs with a wurtzite crystal structure on flat and faceted sapphire substrate (α-Al2O3). The NWs were integrated into fast IR photodetectors showing high on/off ratio of up to ~104 and, to the best of our knowledge, the shortest response times (~100 ms) to IR irradiation with respect to other CdTe based photodetectors. Attempts to create HgxCd1-xTe through cation exchange show initial conversion (~2%) of the crystal, though with significant bandgap narrowing of ~ 55 meV. These findings pave the way for simple and elegant fabrication of CdTe NWs’ based NIR nano-photodetectors, which can be expended to a wide range of Mid-IR and Far-IR photodetectors with small size through bandgap engineering.

Cosmological observations and galaxy dynamics seem to imply that 84% of all matter in the universe is composed of dark matter, which is not accounted for by the Standard Model of particles. The particle nature of dark matter is one of the most intriguing puzzles of our time.
The wealth of knowledge which is and will soon be available from cosmological surveys will reveal new information about our universe. I will discuss how we can use new and complementary data sets to improve our understanding of the particle nature of dark matter.
In particular, galaxy-scale strong gravitational lensing provides a unique way to detect and characterize dark matter on small scales. I will present advances in the analysis of gravitational lenses and identification of small-scale clumps using machine learning. I will introduce the convergence power spectrum as a promising statistical observable that can be extracted from strongly lens images and used to distinguish between different dark matter scenarios, showing how different properties of the dark matter get imprinted at different scales. I will also discuss the different contribution of substructure and line-of-sight structure to perturbations in strong lens images.

Recent discoveries indicate that the genomes of mammalian neurons are enriched for unique epigenetic modifications, including exceptionally high levels of non-CG DNA methylation. In my seminar, I will present our studies defining how a distinctive DNA methylation landscape is established in neurons and exploring how this methylation is read out to control critical gene expression programs. I will discuss the role of gene expression and genome architecture in shaping genomic profiles of non-CG methylation and highlight emerging mechanistic insights into how non-CG methylation and the Rett syndrome protein, MeCP2, work together to control transcription. Finally, I will outline growing evidence that disruption of this regulatory pathway contributes to neurodevelopmental disorders.




Zoom link to join:
https://weizmann.zoom.us/j/96608033618?pwd=SEdJUkR2ZzRBZ3laUUdGbWR1VFJTdz09

Meeting ID: 966 0803 3618
Password: 564068

Host: Dr. Rita Schmidt rita.schmidt@weizmann.ac.il tel: 9070