Ali Javey (Advisor)

Research Advised by Professor Ali Javey

Javey Group:  List of Projects | List of Researchers

BPN887: Edge Recombination Velocity of 2D Materials

Peida Zhao
Matin Amani
2018

Deep study of various 2D transition metal dichalcogenide material edge defects and their respective edge recombination velocity. Also includes investigation into possible passivation schemes to further reduce the ERV of respective 2D materials.

Project end date: 08/07/18

BPN895: Infrared Photodetectors Based on 2D Materials

Matin Amani
James Bullock
Chaoliang Tan
2018

Two-dimensional (2D) materials, particularly black phosphorus (bP), have demonstrated themselves to be excellent candidates for high-performance infrared photodetectors and transistors. However, high-quality bP can be obtained only via mechanical exfoliation from high-temperature- and high-pressure-grown bulk crystals and degrades rapidly when exposed to ambient conditions. Here, we report solution-synthesized and air-stable quasi-2D tellurium (Te) nanoflakes for short-wave infrared (SWIR) photodetectors. We perform comprehensive optical characterization via polarization-resolved...

BPN862: 2D Semiconductor Transistors with 1-Nanometer Gate Length

Sujay B. Desai
Chunsong Zhao
2018

MoS2 transistors with a 1-nm physical gate length using a single-walled carbon nanotube as the gate electrode are demonstrated. These devices exhibit near ideal subthreshold swing ~65 millivolts per decade and an On/Off current ratio ~10^6. This work provides new insight into the ultimate scaling of gate lengths for a FET by surpassing the 5 nm limit often associated with Si technology. Furthermore, the impact of using gate electrodes with limited density of states on the characteristics of nanoscale transistors is studied. Current work involves self- aligned doping of the extension...

BPN822: Monolayer Semiconductor Optoelectronics

Hyungjin Kim
Matin Amani
Der-Hsien Lien
2018

In spite of the great promise they hold for a broad range of applications, two- dimensional (2D) transition metal dichalcogenides (TMDCs) have had a significant drawback of poor photoluminescence (PL) quantum yield (QY) at room temperature. Among a number of studies which have suggested the way to improve QY, superacid treatment, one of the most promising strategies, has enhanced the QY of TMDCs to near 100%. However, insufficient treatment yield and instability of enhanced QY have emerged as critical obstacles to this approach towards practical applications in real devices. In this...

BPN898: A Wearable Microfluidic Sensing Patch for Dynamic Sweat Secretion Analysis

Hnin Y. Nyein
2018

Wearable sweat sensing is a rapidly rising research driven by its promising potential in health, fitness and diagnostic applications. Despite the growing field, major challenges in relation to sweat metrics remain to be addressed. These challenges include sweat rate monitoring for its complex relation with sweat compositions and sweat sampling for sweat dynamics studies. In this work, we present a flexible microfluidic sweat sensing patch that enhances real-time electrochemical sensing and sweat rate analysis via sweat sampling. The device contains a spiral-patterned microfluidic...

BPN901: Roll-to-Roll Gravure Printed Electrode Arrays for Non-Invasive Sensing Applications

Mallika S. Bariya
2018

As recent developments in noninvasive biosensors spearhead the thrust towards personalized health and fitness monitoring, there is a need for high throughput, cost-effective fabrication of flexible sensing components. Towards this goal, we are working on roll-to-roll (R2R) gravure printed electrode arrays that are robust under a diverse range of electrochemical sensing applications, including detection of ions, metabolites, and heavy metals in human perspiration. R2R printed arrays that are suitable for continuous, in situ use are a key step towards enabling large-scale production of...

BPN891: Dopant-Free Asymmetric Heterocontact Silicon Solar Cells with >20% Efficiency

Wenbo Ji
2019

A salient characteristic of solar cells is their ability to subject photo-generated electrons and holes to pathways of asymmetrical conductivity—‘assisting’ them towards their respective contacts. All commercially available crystalline silicon (c-Si) solar cells achieve this by making use of doping in either near-surface regions or overlying silicon-based films. Despite being commonplace, this approach is hindered by several optoelectronic losses and technological limitations specific to doped silicon. A progressive approach to circumvent these issues involves the replacement of...

BPN458: Optical Antenna-Based nanoLED

Kevin Han
Seth Fortuna
Matin Amani
2019

Spontaneous emission has been considered slower and weaker than stimulated emission. As a result, light-emitting diodes (LEDs) have only been used in applications with bandwidth 1 GHz. Spontaneous emission is inefficient because the radiating dipole is much smaller than the wavelength and such short dipoles are poor radiators. By attaching an optical antenna to the radiating dipole at the nanoscale, the emission rate can be significantly increased, enabling high modulation bandwidths theoretically 100 GHz. This project focuses on the physical demonstration of this new type of...

BPN928: Black Phosphorous Based Infrared Light Emitting Diodes

Niharika Gupta
2019

Two-dimensional (2D) materials such as MoS2 and black phosphorous (bP) have shown promise for high performance optoelectronic and electronic applications, due to their naturally terminated surfaces. Unlike the majority of 2D materials, which are only direct bandgap at the monolayer limit, bP maintains a direct bandgap for all thickness, which ranges from 1.4 to 0.3 eV. This property can be leveraged to demonstrate light emitting diodes (LEDs) based on bP/MoS2 heterostructures. High EQE can be...

BPN909: High Quality Synthetic Monolayer Semiconductor

Hyungjin Kim
2019

In recent years, there have been tremendous advancement in the growth of monolayer transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). However, obtaining high photoluminescence quantum yield (PL QY), which is the key figure of merit for optoelectronics, is still challenging in the grown monolayers. Specifically, the as-grown monolayers often exhibit lower PL QY than their mechanically exfoliated counterparts. In this work, we demonstrate synthetic tungsten diselenide (WSe2)...