Opto-electronics at the University of the Algarve

part of the CEOT research unit

Description of work

The research activity is focussed on organic electronics. The main expertise of the group is in electrical characterization techniques, in particular to address impurity states in electronic devices, such as in  Schottky diodes, field effect transistors (MISFETs and TFTs), light emitting diodes (LEDs), solar cells, and also in resistive switching devices for applications in RRAMS.

There is available a broad range of techniques such as: Standard I-V characterization Impedance spectroscopy Deep level transient spectroscopy (DLTS) for low mobility materials Thermal detrapping currents (TSCs) Hall Effect measurements. Magneto-resistance and Magneto-Impedance Time-of flight and other transient techniques

Current research Projects:

Recent major scientific achievements:

- It has been shown that water contamination is the agent responsible for the critical reliability issues in organic based transistors.

- A model to describe thin-film field-effect transistor (TFTs) was developed. This new model successfully describes the basic behavior of organic based transistors. It describes all non-linearities often found in low-mobility (organic) TFTs, including that behavior normally ascribed to contact effects.

- A detailed investigation of polymeric resistance random-access memories (RRAMS) was conducted. For the first time these new type of memory devices were studied using small signal impedance techniques. The physical process behind the switching mechanism was elucidated.

PMeT	Diamond	aT6	TNT
	diamond

Address University of the Algarve,  Campus de Gambelas, FCT,  8005-139 Faro,  PORTUGAL  tel: (+351)  289 800905 fax: +351 289 800

current members name tel. ext. e-mail www Prof. Dr. Henrique Leonel Gomes  7763 7756 www Prof. Dr. Peter Stallinga 7748 www Dr. Alessandra Forner

Title	Authors	Reference	doc
Determining carrier mobility with a metal-insulator-semiconductor structure	P. Stallinga, A.R.V. Benvenho, E.C.P. Smits, S.G.J. Mathijssen, M. Cölle, H.L. Gomes, D.M. de Leeuw	Org. Electr. 9, 735 (2008) doi: 10.1016/j.orgel.2008.05.007
Spatially-resolved photocapacitance measurements to study defects in a-Si:H based p–i–n particle detectors	C. Casteleiro, R. Schwarz, U. Mardolcar, A. Maçarico, J. Martins, M. Vieira, F. Wuensch, M. Kunst, E. Morgado, P. Stallinga, H.L. Gomes	Thin Solid Films 516, 5118 (2008)
Piezoelectric biosensors assisted with electroacoustic impedance spectroscopy: A tool for accurate quantitative molecular recognition analysis	João M. Encarnação, Raul Baltazar, Peter Stallinga, Guilherme N.M. Ferreira	J. Molec. Recognition (2008) doi:10.1002/jmr.907
Metal-insulator-metal transistor	P. Stallinga, V.A.L. Roy, Z.-X. Xu, C.-M. Che	Advanced Materials 20, 2120 (2008) doi: 10.1002/adma.200702525
Space-separated quantum cutting with Si nanocrystals for photovoltaic applications	D. Timmerman, I. Izeddin, P. Stallinga, I.N. Yassievich, T. Gregorkiewicz	Nature Photonics 2, 105 (2008) doi: 10.1038/nphoton.2007.279
Dynamics of threshold voltage shifts in organic and amorphous silicon field-effect transistors	S. Mathijssen, M. Cölle, H. Gomes, E.C.P. Smits, B. de Boer, I. McCulloch, P.A. Bobbert and D.M. de Leeuw	Advanced Materials doi: 10.1002/adma.200602798
Detection of chloroform with a sensor array consisting of electrochemically deposited polythiophenes films: Processes governing the electrical response	E.R Carvalho, A.A Correa, N.C. Filho, O.N Oliveira, H.L. Gomes, H.C. Mattoso, L. Martin-Neto	Sensor Lett. 5, 374 (2007)
Switching in polymeric resistance random-access memories (RRAMS)	H.L. Gomes, A.R.V. Benvenho, D.M. de Leeuw, M. Cölle, P. Stallinga, F. Verbakel and D.M. Taylor	Organic Electronics 9, 119 (2008) doi:10.1016/j.orgel.2007.10.002
Reproducible resistive switching in nonvolatile organic memories	Frank Verbakel, Stefan C. J. Meskers, René A. J. Janssen. Henrique L. Gomes, Michael Cölle, Michael Büchel, and Dago M. de Leeuw	Appl. Phys. Lett. 91,1 (2007)
Voltage- and light-induced hysteresis effects at the high-k dielectric- poly(3-hexylthiophene) interface	J. Lancaster, D. M. Taylor, P. Sayers  and H.L. Gomes	Appl. Phys. Lett. 90, 103513 (2007)
Polymer nano-composite Field Effect Transistors	Zong-Xiang Xu, V.A.L. Roy, Peter Stallinga, Michele Muccini, Chi-Ming Che	Appl. Phys. Lett. 90, 223509 (2007)
Metal contacts in thin-film transistors	P. Stallinga, H.L. Gomes	Org. Electr. 8, 300 (2007)
Thin-film field-effect transistors: the effects of traps on the bias and temperature dependence of field-effect mobility, including the Meyer-Neldel rule	P. Stallinga, H.L. Gomes	Org. Electr. 7, 592 (2006)
Modelling electrical characteristics of thin-film field-effect transistors. II: Effects of traps and impurities.	P. Stallinga, H.L. Gomes	Synthetic Metals 156, 1316 (2006)
Modelling electrical characteristics of thin-film field-effect transistors. I: Trap-free materials.	P. Stallinga, H.L. Gomes	Synthetic Metals 156, 1305 (2006)
Influence of electrolytes in the QCM response: Discrimination and quantification of the interference to correct microgravimetric data.	João M. Encarnação, P. Stallinga, Guilherme N.M. Ferreira	Biosensors and Bioelectronics 22, 1351 (2007)
Electrical instabilities in organic semiconductors caused by trapped supercooled water	H.L. Gomes, P. Stallinga, M. Cölle, D.M. de Leeuw, and F. Biscarini	Appl. Phys. Lett. 88, 082101 (2006)
Traps states as an explanation for the Meyer-Neldel rule in organic semiconductors	P. Stallinga, H.L. Gomes	Org. Electr. 6, 137 (2005)
Tetracene-based organic light-emitting transistors: optoelectronic properties and electron injection mechanism	C. Santato, R. Capelli, M.A. Loi, M. Murgia, F. Cicoira, V.A.L. Roy, P. Stallinga, R. Zamboni, C. Rost, S.F. Karg, and M. Muccini	Synthetic Metals 146, 329 (2004)
Bias-Induced threshold voltages shift in thin-film organic transistors	H.L. Gomes, P. Stallinga, F. Dinelli, M. Murgia, F. Biscarini, D.M. De Leeuw, T. Muck, J. Geurts, L.W. Molenkamp, V. Wagner	Appl. Phys. Lett. 84, 3184 (2004)
Electronic transport in field-effect transistors of sexithiophene	P. Stallinga, H.L. Gomes, F. Biscarini, M. Murgia, D.M. de Leeuw	J. Appl. Phys. 96, 5277 (2004)
Interface state mapping in a Schottky barrier of the organic semiconductor terrylene	P. Stallinga, H.L. Gomes, M. Murgia, K. Müllen	Org. Electr. 3, 43 (2002)
Minority-carrier effects in poly-phenylenevinylene as studied by electrical characterization	P. Stallinga, H.L. Gomes, H. Rost, A.B. Holmes, M.G. Harrison, and R.H. Friend	J. Appl. Phys. 89, 1713 (2001)
Analysis of deep levels in a phenylenevinylene polymer by transient capacitance methods	H.L. Gomes, P. Stallinga, H. Rost, A.B. Holmes, M.G. Harrison, and R.H. Friend	Appl. Phys. Lett. 74, 1144 (1999)

Title	Conference	Authors	Reference	pdf
Study of trap states in zinc oxide (ZnO) thin films for electronic applications		C. Casteleiro, H.L. Gomes, P. Stallinga, L. Bentes, R. Ayouchi, R. Schwarz	Journal of Non-Crystalline Solids 354, 2519 (2008)
Spatially-Resolved Photocapacitance Measurements to Study Defects in a-Si:H Based p-i-n Particle Detectors	E-MRS, Strasbourg 2006	C. Casteleiro, R. Schwarz, A. Maçarico, J. Martins, M. Vieira, F. Wuensch, M. Kunst, E. Morgado, P. Stallinga, H. Gomes	submitted
The effect of water related traps on the reliability of organic based transistors		H.L. Gomes, P. Stallinga, M. Colle, F. Biscarini, and D.M. de Leeuw	J. Non-Crystalline Solids 352, 1761 (2006)
Organic Materials for Active Layers in Transistors: Study of the Electrical Stability Properties	Materiais 2005, Aveiro 2005	H.L. Gomes, P. Stallinga, and D.M. de Leeuw	Mater. Sci. Forum 514-516, 33 (2006)
Light-emitting thin-film field-effect transistors	invited talk at ASpect 2, Warsaw	P. Stallinga, H.L. Gomes	Optica Applicata 36, 373 (2006)
Meta-stability effects in organic based transistors	SPIE, Optics and Photonics 2005, San Diego (USA)	H.L. Gomes, P. Stallinga, M. Murgia, F. Biscarini, T. Muck, V. Wagner, E. Smits, D.M. de Leeuw	SPIE Int. Soc. Opt. Eng. vol. #5940-20	(CamReady)
Meta-stability effects in organic based transistors	Technologies for Polymer Electronics TPE04, Rudolstadt 2004	H.L. Gomes, P. Stallinga, F. Dinnelli, M. Murgia, F. Biscarini, D.M. De Leeuw	Proceedings of the Intern. Symposium "Technologies of Polymer Electronics TPE 04", Rudolstadt/Germany, 28.-30.09.2004, p. 105-110
Explanation of the Meyer-Neldel rule	Technologies for Polymer Electronics TPE04, Rudolstadt 2004.	P. Stallinga and H.L. Gomes	Proceedings of the Intern. Symposium "Technologies of Polymer Electronics TPE 04", Rudolstadt/Germany, 28.-30.09.2004, p. 125-129
A microelectrode impedance method to measure interaction of cells	IEEE Sensors 2004, Vienna, 2004	H.L. Gomes, R.B. Leite, R. Afonso, P. Stallinga and M.L. Cancela	Proceedings of IEEE Sensors 2004, Vienna, p. 1011-1013 (2004)
Detection of explosive vapors using organic thin-film transistors	IEEE Sensors 2004, Vienna, 2004	E. Bentes, H.L. Gomes, P. Stallinga	Proceedings of IEEE Sensors 2004, Vienna, p. 766-769 (2004)
TNT sensor using organic thin film transistors	8th Portuguese-Spanish Congress in Electrical Engineering (2003)	E. Bentes, R. Luis, H.L. Gomes, P. Stallinga, L. Moura	8th Portuguese-Spanish Congress in Electrical Engineering (2003), 8CLEEE
Electrical characterization of organic-based transistors: stability issues	invited talk at PAT conference, Forth Lauderdale, USA, 2003.	H.L. Gomes, P. Stallinga, F. Dinelli, M. Murgia, F. Biscarini, D.M. de Leeuw, M. Muccini, K. Müllen	Polymers for Adv. Technol. 16, 227 (2005)
Electrical characterization of pn-junctions of PPV and silicon	ICSM, Gastein, Austria	P. Stallinga, H.L. Gomes, A. Charas, J. Morgado, and L. Alcácer	Synth. Metals 121, 1535 (2001)
Electrical characterization of CVD diamond-n+silicon junctions	Diamond and Related Materials, Pargue 2001	A.M. Rodrigues, H.L. Gomes, P. Stallinga, L. Pereira, E. Pereira	Diamond and Related Materials 10, 858 (2001)
Determination of deep and shallow levels in conjugated polymers by electrical methods	ICDS, Berkeley, California 1999	P. Stallinga, H.L. Gomes, H. Rost, A.B. Holmes, M.G. Harrison, R.H. Friend, F. Biscarini, C. Taliani, G.W. Jones, D.M. Taylor	Physica B 273-274, 923 (1999)
Electronic levels in MEH-PPV	ICEL-2, Sheffield, England	P. Stallinga, H.L. Gomes, H. Rost, A.B. Holmes, M.G. Harrison, and R.H. Friend,	Synthetic Metals 111, 535 (2000)
Electrical Study of Impurity States in Conjugated Polymers	ICSM, Montpellier, France	P. Stallinga, H.L. Gomes, G.W. Jones and D.M. Taylor	Synthetic Metals 101, 496 (1999)
Electrical Characterization of Semiconducting Polymers	Jaszowiecz XXVII, Poland	P. Stallinga, H.L. Gomes, G.W. Jones, and D.M. Taylor	Acta Phys. Pol. A 94, 545 (1998)

III: Books

Title	Author	Reference	Link
Electrical Characterization of Organic Electronic Materials and Devices	P. Stallinga	Wiley ISBN: 978-0-470-75009-4 Hardcover 316 pages

Part I: Bipolar Devices	Part II: MOS-FETs	Part III: TFTs

Presentations:
SELOA Summer School (2000), Peter Stallinga (power point presentation), part I, part II
 

more theory: when I (P.S.) was working in Berkeley, I wrote the following  manual for MCD (magnetic circular dichroism of absorption). It might be  useful to others:  mcd_4dum.pdf

Datasheets/Manuals of electronic equipment of OptoEl

Equipment	Brand	model(s)	pdf
Lock-in detector	Stanford	SR830
Digital Oscilloscope	Tektronix	TDSxxx
Multimeter	Thurlby Thandar	TTi 1604
Source/Meter	HP (Agilent)	6614C
PicoAmp Meter	Keithley	487
Multimeter	Keithley	2000
Picoammeter/Voltage source	Keithley	6487
Programmable Power Supply	Thurlby Thandar	PL330DP
Pulse Generator (20 ns, 100V)	Agilent	8114A
Network Anlyzer	Hewlet Packard	8712C
	Keithley	6407
Temperature Controller	Oxford	ITC 601
Monochromator	Jobin Yvon	TRIAX 320
		ALG 3102
		RSA 2203A
RCL bridge	Fluke	PM6306

more information:

• University of the Algarve
• CEOT (centro de electrónica, optoelectrónica e telecomunicações)
• BioFET