Poster REU 2016

3-hydroxyphenalenone (3-HPLN) was chosen as the source material to prepare organic thin films on Al2O3 substrates

Films were deposited using thermal evaporation under high vacuum. (EvoVac)

Substrate temperature was adjusted to control the film morphology

Atomic Force Microscopy (AFM) was used to measure the surface morphology of the thin films

This work was supported by the National Science Foundation (NSF) through the Centers of Research Excellence in Science and Technology (CREST, HRD-1345163), and by the Nebraska Materials Research Science and Engineering Center (MRSEC, DMR-1420645).

Dr. Yuewei Yin, Kishan Kumar Sinha, Xiaozhe Zhang; Physics and Astronomy, UNL

Thank you to UNL Physics and Astronomy Department, for hosting this internship.

Organic electronics are gaining relevance due to their flexibility and low cost. In particular, organic thin films play critical roles in these applications for replacing certain inorganic counter parts.

Preparing organic thin films of smooth morphology is necessary for application. Here we study the effect of growth conditions on film morphology in physical vapor deposition processes.

Abstract

Purpose

Comparison of 3-HPLN and Croconic Acid

Analysis

Conclusion

Acknowledgements

Procedure Clean the Al2O3 substrate which is then placed inside the

chamber. Pump down the chamber to high vacuum (110 -7 Torr) Begin to heat the organic source to the sublimation point;

cooling down the substrate if needed. Open the shutter to allow the organic molecules to deposit onto

the substrate. AFM for morphology characterization.

Instrumentation

References1 Slashgear.comhttp://www.slashgear.com/lg-pumps-8-7bn-into-oled-for-your-car-tv-and-wrist-27416167/

Line scan of the images at RT (left) and -80 °C (right).

EvoVac Deposition:High vacuum for

sublimation of organic materials.

Variable substrate temperature from -160C to 200C for controlling the film growth

3-HPLN at -15C:• Thickness: 40nm

• Abled to see some holes on the surface.

3-HPLN at RT:• Thickness: 40nm

• Grown close together, not smooth

3-HPLN at -80C• Thickness: 40nm

• Grew in Island style wouldn’t be a good surface

A Study of the Morphology of Organic Thin Films:

Nicole Lopez1, Xuanuan Jiang2, Dr. Xiaoshan Xu2

1Department of Physics, California State University, San Bernardino, CA, USA2Department of Physics and Astronomy at University of Nebraska-Lincoln, NE, USA

Surface Morphologies

Croconic Acid(CA) at -30C: Covered the whole

substrate surface Has low roughness

of 3.5nm.

3-HPLN at -30C:• Thickness: 40nm

• Rough but has a nearly continues surface.

Atomic Force Microscope(AFM):Scanning probe to

determine the surface morphology

Surface roughness, coverage can be found from the AFM images

Vaporized material

Deposition of thin film

Source Material Heater

Vacuum Chamber

Source Holder3-HPLN at -30C: Covered most of

the surface, can observe some holes.

Has high roughness of 50nm .

Nebraska

MRSEC

The picture to the left shows how the flexibility of the organic thick films may impact and even revolutionize the consumer electronics1.

Liquid Nitrogen Reservoir

1.0µm

890nm

Substrate Temperature Coverage Shape Size

Room Temp 97% Round/oval 268 nm

-15 °C 68%Oval, pointed

in various directions

247 nm

-30 °C 88% Round, slanted 223 nm

-80 °C 75%Needle shaped,

random orientation

251 nm

Best surface at various substrate temperature was -30 °C.At -30 °C 3-HPLN covers 88% of the surface but has a

roughness of 50 nm. A comparison of Croconic acid and 3-HPLN found that

Croconic acid had a smoother surface, with 97% Coverage and 3.5nm Roughness.

Substrate

By using the AFM, we obtained the images of the surface of the

thin films to analyze how various sub. Temperatures effected the

morphologies