Interplay between vacuum-grown monolayers of alkyl phosphonic acids and the performance of organic transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene

Stuart Hannah, Javier Cardona, Dimitrios A. Lamprou, Pavol Sutta , Peter Baran, Afra Al Ruzaiqi, Karen Johnston, Helena Gleskova

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Monolayers of six alkyl phosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum deposited monolayers improved with increasing length of the aliphatic tail. At the same time, FTIR measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by Density Functional Theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ~17.5 mJ/m2 with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in the transistor performance was observed with increasing length of the aliphatic tail. Going from C8 to C18 the mean threshold voltage decreased from ‒1.37 to ‒1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm2/Vs, the off-current decreased from ~ 8×10-13 to ~ 3×10-13 A, and for transistors with L = 30 um the on-current increased from ~ 3×10-8 to ~ 2×10-6 A, and the on/off current ratio increased from ~ 3×104 to ~ 4×106. Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely ‘dry’ fabrication route for ultra-thin dielectrics and low-voltage organic transistors.
LanguageEnglish
Pages25405-25414
Number of pages10
JournalACS Applied Materials and Interfaces
Volume8
Issue number38
DOIs
Publication statusPublished - 28 Sep 2016

Fingerprint

Phosphorous Acids
Thiophenes
Thiophene
Monolayers
Transistors
Vacuum
Acids
Organic field effect transistors
Vacuum evaporation
Electric potential
Time measurement
Threshold voltage
Interfacial energy
Density functional theory
Surface roughness
Fabrication
Molecules
Air

Keywords

  • organic field-effect transistor
  • alkyl phosphonic acids
  • monolayer
  • DNTT
  • bias stress
  • vacuum-grown
  • low-voltage operation

Cite this

@article{dac87dacc508488586d5dc6a67f421af,
title = "Interplay between vacuum-grown monolayers of alkyl phosphonic acids and the performance of organic transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene",
abstract = "Monolayers of six alkyl phosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum deposited monolayers improved with increasing length of the aliphatic tail. At the same time, FTIR measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by Density Functional Theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ~17.5 mJ/m2 with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in the transistor performance was observed with increasing length of the aliphatic tail. Going from C8 to C18 the mean threshold voltage decreased from ‒1.37 to ‒1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm2/Vs, the off-current decreased from ~ 8×10-13 to ~ 3×10-13 A, and for transistors with L = 30 um the on-current increased from ~ 3×10-8 to ~ 2×10-6 A, and the on/off current ratio increased from ~ 3×104 to ~ 4×106. Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely ‘dry’ fabrication route for ultra-thin dielectrics and low-voltage organic transistors.",
keywords = "organic field-effect transistor, alkyl phosphonic acids, monolayer, DNTT, bias stress, vacuum-grown, low-voltage operation",
author = "Stuart Hannah and Javier Cardona and Lamprou, {Dimitrios A.} and Pavol Sutta and Peter Baran and {Al Ruzaiqi}, Afra and Karen Johnston and Helena Gleskova",
year = "2016",
month = "9",
day = "28",
doi = "10.1021/acsami.6b08426",
language = "English",
volume = "8",
pages = "25405--25414",
journal = "ACS Applied Materials and Interfaces",
issn = "1944-8244",
publisher = "American Chemical Society",
number = "38",

}

TY - JOUR

T1 - Interplay between vacuum-grown monolayers of alkyl phosphonic acids and the performance of organic transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene

AU - Hannah, Stuart

AU - Cardona, Javier

AU - Lamprou, Dimitrios A.

AU - Sutta , Pavol

AU - Baran, Peter

AU - Al Ruzaiqi, Afra

AU - Johnston, Karen

AU - Gleskova, Helena

PY - 2016/9/28

Y1 - 2016/9/28

N2 - Monolayers of six alkyl phosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum deposited monolayers improved with increasing length of the aliphatic tail. At the same time, FTIR measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by Density Functional Theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ~17.5 mJ/m2 with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in the transistor performance was observed with increasing length of the aliphatic tail. Going from C8 to C18 the mean threshold voltage decreased from ‒1.37 to ‒1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm2/Vs, the off-current decreased from ~ 8×10-13 to ~ 3×10-13 A, and for transistors with L = 30 um the on-current increased from ~ 3×10-8 to ~ 2×10-6 A, and the on/off current ratio increased from ~ 3×104 to ~ 4×106. Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely ‘dry’ fabrication route for ultra-thin dielectrics and low-voltage organic transistors.

AB - Monolayers of six alkyl phosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum deposited monolayers improved with increasing length of the aliphatic tail. At the same time, FTIR measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by Density Functional Theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ~17.5 mJ/m2 with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in the transistor performance was observed with increasing length of the aliphatic tail. Going from C8 to C18 the mean threshold voltage decreased from ‒1.37 to ‒1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm2/Vs, the off-current decreased from ~ 8×10-13 to ~ 3×10-13 A, and for transistors with L = 30 um the on-current increased from ~ 3×10-8 to ~ 2×10-6 A, and the on/off current ratio increased from ~ 3×104 to ~ 4×106. Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely ‘dry’ fabrication route for ultra-thin dielectrics and low-voltage organic transistors.

KW - organic field-effect transistor

KW - alkyl phosphonic acids

KW - monolayer

KW - DNTT

KW - bias stress

KW - vacuum-grown

KW - low-voltage operation

UR - http://pubs.acs.org/journal/aamick

U2 - 10.1021/acsami.6b08426

DO - 10.1021/acsami.6b08426

M3 - Article

VL - 8

SP - 25405

EP - 25414

JO - ACS Applied Materials and Interfaces

T2 - ACS Applied Materials and Interfaces

JF - ACS Applied Materials and Interfaces

SN - 1944-8244

IS - 38

ER -