Ali Javey (Advisor)

Research Advised by Professor Ali Javey

Javey Group:  List of Projects | List of Researchers

BPN777: Nonepitaxial Growth of Single Crystalline III-V Semiconductors onto Insulating Substrates

Kevin Chen
Sujay Desai
2017

III-V semiconducting materials have many characteristics such as high electron mobilities and direct band. gaps that make them desirable for many electronic applications including high performance transistors and solar cells. However, these materials generally have a high cost of production which significantly limits their use in many commercial applications. We aim to explore new growth methods which can grow high quality crystalline III-V films, using InP as an example substrate, onto non-epitaxial substrates. In addition to excellent crystal quality, critical considerations...

BPN883: Microchannel Contacting of Crystalline Silicon Solar Cells

James Bullock
Mark Hettick
2017

There is tremendous interest in reducing losses caused by the metal contacts in silicon photovoltaics, particularly the optical and resistive losses of the front metal grid. One commonly sought after goal is the creation of high aspect-ratio metal fingers which provide an optically narrow and low resistance pathway to the external circuit. Currently, the most widely used metal contact deposition techniques are limited to widths and aspect-ratios of ~40 μm and ~0.5, respectively. In this study, we introduce the use of a micropatterned polydimethylsiloxane encapsulation layer to form...

BPN818: Fully-Integrated Wearable Sensor Arrays for Multiplexed In Situ Perspiration Analysis

Hnin Y.Y. Nyein
Wei Gao
Mallika Bariya
2017

A flexible and wearable microsensor array is described for simultaneous multiplexed monitoring of heavy metals in human body fluids. Zn, Cd, Pb, Cu, and Hg ions are chosen as target analytes for detection via electrochemical square wave anodic stripping voltammetry (SWASV) on Au and Bi microelectrodes. The oxidation peaks of these metals are calibrated and compensated by incorporating a skin temperature sensor. High selectivity, repeatability, and flexibility of the sensor arrays are presented. Human sweat and urine samples are collected for heavy metal analysis, and measured results...

BPN879: A Wearable Impedance-Based Microfluidic Sensor for Sweat Rate Monitoring

Li-Chia Tai
2017

A flexible and wearable sensor is presented for real-time monitoring of localized perspiration rate of human subjects. These sweat rate measurements are validated through controlled syringe pumping and a commercial sweat collector. Real-time on-body perspiration rate evaluation of human subjects is performed through cycling experiments to examine the change in sweat rate with different power output. Since it has been shown that the concentrations of a large number of sweat biomarkers are strongly related to the variation of a subject's perspiration rate, this platform is anticipated...

BPN881: Strain-Engineered Growth of Two-Dimensional Materials

Geun Ho Ahn
Matin Amani
2018

The application of strain to semiconductors allows for controlled modification of their band-structure. This principle is employed for the manufacturing of devices ranging from high- performance transistors to solid- state lasers. Traditionally, strain is typically achieved via growth on lattice-mismatched substrates. For two- dimensional (2D) semiconductors, this is not feasible as they typically do not interact epitaxially with the substrate. Here, we demonstrate controlled strain engineering of 2D semiconductors during synthesis by utilizing the thermal coefficient of expansion (...

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...