Pentacene-Based Organic Thin Film Transistors for Ammonia Sensing

Dept. of Photonics, Nat. Chiao Tung Univ., Hsinchu, Taiwan
IEEE Sensors Journal (Impact Factor: 1.76). 04/2012; 12(3):594 - 601. DOI: 10.1109/JSEN.2011.2121901
Source: IEEE Xplore


Non-invasive ammonia sensors are attractive alternatives for the diagnoses of a variety of chronic diseases such as liver cirrhosis and renal failure. A low cost pentacene-based organic thin film transistor (OTFT) fabricated by a novel and simple process was demonstrated to be highly sensitive and specific for ammonia gas. Various measurement parameters that reflected OTFT device characteristics for ammonia detection were investigated. Significant variations of the turn-on current, intrinsic mobility, and threshold voltage ( V th) were observed while subthreshold swing ( S . S .) was almost unchanged to the alteration of ammonia concentration. The OTFT device detected 0.5 ~ 5 ppm concentration ammonia gas at room temperature, which is in the critical range that can distinguish between healthy person and paticents with liver cirrhosis and renal failure. The sensitivity of the device was further enhanced following a simple UV irradiation treatment to modify the functional groups on poly(methyl methacrylate) (PMMA) dielectric layer. Possible interference for ammonia detection such as humidity effect and selectivity among nitrogen, alcohol, carbon dioxide, acetone, methane and ammonia were also examined. We concluded that the proposed pentacene-based OTFT is a promising device for the future application in non-invasive medical diagnoses.

Download full-text


Available from: Yuh-Shyong Yang,
1 Follower
51 Reads
  • Source
    • "Furthermore, hydroxyl groups in polymers have been reported to have the ability to interact with ammonia to form structure like ammonia water, thus the trapped ammonia at the dielectric surface may not be removed easily under the environment of dry air [32]. For PMMA dielectric, the dipole moment of the –COOCH 3 has the ability to absorb NH 3 molecules [31], while such interactions will not happen between ammonia and benzene rings. In addition, the polarities of PVA, PMMA and PVP are all higher than that of PS, which indicates dipole–dipole interactions can occur much more frequently between the above three dielectrics and polar ammonia. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Ammonia (NH3) gas sensors based on pentacene organic field-effect transistors (OFETs) are fabricated using polymers as the dielectric. Compared with those incorporating poly(vinyl alcohol), poly(4-vinylphenol) or poly(methyl methacrylate) dielectric, a low detect limitation of 1 ppm and enhanced recovery property are obtained for OFETs with polystyrene (PS) as gate dielectric. By analyzing the morphologies of pentacene and electrical characteristics of the OFETs under various concentrations of NH3, the variations of the sensing properties of different dielectrics based OFET-sensors are proved to be mainly caused by the diversities of dielectric/pentacene interfacial properties. Furthermore, low surface trap density and the absence of polar groups in PS dielectric are ascribed to be responsible for the high performance of NH3 sensors.
    Organic Electronics 09/2013; 14(12):3453. DOI:10.1016/j.orgel.2013.09.018 · 3.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we present the implementation and measurement results of all analog building blocks of an organic smart sensor system on foil. The presented building blocks are a 1D and a 2D 4 $\times$4 pixel flexible capacitive touch sensor with a sample rate of 1.5 kS/s, a DC-connected two-stage opamp with a 20 dB DC gain, a Dickson DC-DC up-converter with output bias voltages up to 60 V and down to $-$ 40 V which are used as a bias voltage in the other building blocks, and a $\Delta\Sigma$ ADC with a 26.5 dB precision and a band width of 15.6 Hz. The sensors, the opamp, the DC-DC converter and the ADC respectively consume 6 $\mu{\hbox{A}}$, 15 $\mu{\hbox{A}}$ , 1 $\mu{\hbox{A}}$ and 100 $\mu{\hbox{A}}$ from a 15 V power supply.
    IEEE Journal of Solid-State Circuits 07/2012; 47(7):1712-1720. DOI:10.1109/JSSC.2012.2191038 · 3.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have increased organic field-effect transistor (OFET) NH(3) response using tris(pentafluorophenyl)borane (TPFB) as a receptor. OFETs with this additive could detect concentrations of 450 ppb v/v, with a limit of detection of 350 ppb, the highest sensitivity reported to date for semiconductor films; in comparison, when triphenylmethane (TPM) or triphenylborane (TFB) was used as an additive, no obvious improvement in the sensitivity was observed. These OFETs also showed considerable selectivity with respect to common organic vapors and stability toward storage. Furthermore, excellent memory of exposure was achieved by keeping the exposed devices in a sealed container stored at -30 °C, the first such capability demonstrated with OFETs.
    Journal of the American Chemical Society 08/2012; 134(36):14650-3. DOI:10.1021/ja305287p · 12.11 Impact Factor
Show more