Mork Family Department ofChemical Engineering and Materials Science

Si JFET-Controlled Carbon Nanotube Field Emitter ArraysQiong Shui1, Martin Gundersen1,2, Ryan J. Umstattd3, Chongwu Zhou2, Alan M. Cassel4, lJonathan Shaw5, and David S. Y. Hsu5

1Department of Chemical Engineering and Materials Science,University of Southern California, Los Angeles, CA, 90089-02712Department of Electrical Engineering – Electrophysics,University of Southern California, Los Angeles, CA, 90089-0271

3Physics Department, Naval Postgraduate School, Monterey, CA, 939434Center for Nanotechnology, NASA Ames Research Center, Moffett Field, CA, 94035

5Naval Research Laboratory, Washington, DC, 20375

IntroductionIntroductionIntroductionIntroduction Fabrication ProcessFabrication ProcessFabrication ProcessFabrication Process MeasurementsMeasurementsMeasurementsMeasurements

Simulation Results for Si JFETsSimulation Results for Si JFETsSimulation Results for Si JFETsSimulation Results for Si JFETs

Future WorkFuture WorkFuture WorkFuture Work

0

100

200

300

400

500

600

0 5 10 15 20Drain Voltage (V)

Id (

A/c

m^2

)

Vgs=0 V

Vgs=-4 V

Vgs=-2 V

Vgs=-6 VVgs=-8 V

1. C. A. Spindt, "A thin-film field-emission cathode," J. Appl. Phys., vol. 39, pp. 3504-3505, 1968.

2. T. Utsumi, "Keynote address vacuum microelectronics: What's new and exciting," IEEE Transaction on Electron Devices, vol. 38, pp. 2276-2283, 1991.

3. http://other.nrl.navy.mil/CREBWorkShop/Jensen.pdf

Ion Projected Range

1.0E+18

1.0E+19

1.0E+20

1.0E+21

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Depth (micrometer)

Impu

rity

Con

cent

ratio

n (a

tom

s/cm

3)

CNTs Field Emitter Applications

1. Providing the electron beam(s) inside of flat panel field emission displays(FED) [3]• lower power consumption• Wider view angles• Viewable from any angle with no change in brightness, contrast or color• Faster response time

2. Providing the electron beam in vacuum microwave amplifiers/oscillators

3. Providing the electron beam for charge neutralization when using ion thrusters for propulsion in space

Motivation1. The introduction of Spindt microtip [1] cold cathodes has led to

great interest in the pursuit of electron beam sources for flat panel display and vacuum microelectronic devices

2. CNTs are the closest one that have “ideal” field emitters[2]

• Stable at high temperature

• Have high electrical and thermal conductivity

• Exhibit ballistic electron transport.

3. Stability and lifetime are two important issues to be addressed before field emitters find wide applications

Active devices, JFETs, were proposed in our study to control the stability of the emission current of CNTs

ReferencesReferencesReferencesReferences

The left figure (Fig. 1) shows Si post JFET structure for simulation of breakdown voltages of JFETs. The right figure (Fig. 2) shows the breakdown voltage of the JFETs when ion implantation energy are at 150 keV and 200 keV, respectively

Fig. 3 Boron impurity distribution in Si simulated by SRIM-2003 at an ion implantation energy of 150keV and a dose of 51015/cm3.

Fig. 4 Drain Voltage vs. Id for the built-in JFET at different Vgs.

(a). Deposit Cr/Au (b). Etch Si post by Electron Cyclotron Resonance etcher

(e). Deposit SiO2 by PECVD and Cr to pattern the extraction gate

(g). Etch Cr and SiO2 to open windows for emitter sites

(i). Grow CNTs by PECVD at 700 °C

(h). Deposit the buffer layer Cr (40nm) and the catalyst layer Ni (20nm) for CNTs growth

(f). Define the control gate

(c). Boron was ion implanted to form P+ regions

The Pulsed Power Group of USC thanks the Air Force Office of Scientific Research for their generous support.

AcknowledgementAcknowledgementAcknowledgementAcknowledgement

0.0E+00

1.0E-08

2.0E-08

3.0E-08

4.0E-08

5.0E-08

6.0E-08

0 2 4 6 8 10

Voltage (V)

Cur

rent

(A

)

P+Cr

SiO2

N- Si substrate N+

Extraction Gate

Control GateFig. 5 Leakage current vs. the voltage between the extraction gate and the control gate. The thickness of SiO2 is 1 m. the

calculated resistivity of our deposited SiO2 at 25 °C is

about 61012 Ω-cm.

Fig. 7 SEM images(left and right) of vertically aligned CNTs grown on Si post JFETs. The tilt angle for taking the images is 85 °.

Fig. 6 SEM image shows the structure after Cr and SiO2 were etched through the patterned 2 m diameter emitter sites

• Test the emission current of CNT emitter arrays and its stability

• Optimize the fabrication process