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Charge transport mechanisms and memory effects in amorphous TaNx thin films.

Spyropoulos-Antonakakis N, Sarantopoulou E, Drazic G, Kollia Z, Christofilos D, Kourouklis G, Palles D, Cefalas AC - Nanoscale Res Lett (2013)

Bottom Line: However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly.The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment.Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

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C-AFM measurements of a-TaNx. (a) Positive I-V curves (solid lines) of TaNx deposited on Au for four different points fitted by the space-charge-limited current (SCLC) model (dash lines). (b) Negative I-V curves (solid lines) of TaNx deposited on Au for the same points presented in (a) fitted by the SCLC model (dash lines). (c) Positive I-V curves of TaNx deposited on Si for three different points. The conductive part of the I-Vs exhibits an almost parabolic to almost ohmic behavior (d) Negative I-V curves of TaNx deposited on Si for the points presented in (b). In all I-Vs, the leakage current is quite high, displaying also a very noisy profile.
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Figure 5: C-AFM measurements of a-TaNx. (a) Positive I-V curves (solid lines) of TaNx deposited on Au for four different points fitted by the space-charge-limited current (SCLC) model (dash lines). (b) Negative I-V curves (solid lines) of TaNx deposited on Au for the same points presented in (a) fitted by the SCLC model (dash lines). (c) Positive I-V curves of TaNx deposited on Si for three different points. The conductive part of the I-Vs exhibits an almost parabolic to almost ohmic behavior (d) Negative I-V curves of TaNx deposited on Si for the points presented in (b). In all I-Vs, the leakage current is quite high, displaying also a very noisy profile.

Mentions: By fixing the tip on individual nanodomains of a-TaNx films deposited on Au or Si, the local I-V characteristics are repeatedly recorded with the voltage being swept from -10 to 10 V. In Figure 5, the I-V curves for forward and reverse bias voltages at several local points are shown for TaNx deposited on Au (Figure 5a,b) and Si (Figure 5c,d). At first glance, comparing the I-Vs of the nanodomains, which are located on the same film, small or large differences in conductivity and threshold voltage are observed for both films. However, the shape of the I-Vs is quite similar, indicating that the conduction mechanism is the same for all nanodomains located on the same film. Comparing now, the I-Vs between the two films, it is seen that the threshold voltage for the leakage current at the point contacts of Figure 5a is higher than 3.5 V, while for the point contacts in Figure 5c, the threshold voltage does not exceed 1 V. It is also noticed that there is a different response of the I-Vs in the two metal-dielectric-metal devices.


Charge transport mechanisms and memory effects in amorphous TaNx thin films.

Spyropoulos-Antonakakis N, Sarantopoulou E, Drazic G, Kollia Z, Christofilos D, Kourouklis G, Palles D, Cefalas AC - Nanoscale Res Lett (2013)

C-AFM measurements of a-TaNx. (a) Positive I-V curves (solid lines) of TaNx deposited on Au for four different points fitted by the space-charge-limited current (SCLC) model (dash lines). (b) Negative I-V curves (solid lines) of TaNx deposited on Au for the same points presented in (a) fitted by the SCLC model (dash lines). (c) Positive I-V curves of TaNx deposited on Si for three different points. The conductive part of the I-Vs exhibits an almost parabolic to almost ohmic behavior (d) Negative I-V curves of TaNx deposited on Si for the points presented in (b). In all I-Vs, the leakage current is quite high, displaying also a very noisy profile.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4016540&req=5

Figure 5: C-AFM measurements of a-TaNx. (a) Positive I-V curves (solid lines) of TaNx deposited on Au for four different points fitted by the space-charge-limited current (SCLC) model (dash lines). (b) Negative I-V curves (solid lines) of TaNx deposited on Au for the same points presented in (a) fitted by the SCLC model (dash lines). (c) Positive I-V curves of TaNx deposited on Si for three different points. The conductive part of the I-Vs exhibits an almost parabolic to almost ohmic behavior (d) Negative I-V curves of TaNx deposited on Si for the points presented in (b). In all I-Vs, the leakage current is quite high, displaying also a very noisy profile.
Mentions: By fixing the tip on individual nanodomains of a-TaNx films deposited on Au or Si, the local I-V characteristics are repeatedly recorded with the voltage being swept from -10 to 10 V. In Figure 5, the I-V curves for forward and reverse bias voltages at several local points are shown for TaNx deposited on Au (Figure 5a,b) and Si (Figure 5c,d). At first glance, comparing the I-Vs of the nanodomains, which are located on the same film, small or large differences in conductivity and threshold voltage are observed for both films. However, the shape of the I-Vs is quite similar, indicating that the conduction mechanism is the same for all nanodomains located on the same film. Comparing now, the I-Vs between the two films, it is seen that the threshold voltage for the leakage current at the point contacts of Figure 5a is higher than 3.5 V, while for the point contacts in Figure 5c, the threshold voltage does not exceed 1 V. It is also noticed that there is a different response of the I-Vs in the two metal-dielectric-metal devices.

Bottom Line: However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly.The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment.Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute, 48 Vassileos Constantinou Avenue, Athens 11635, Greece. esarant@eie.gr.

ABSTRACT
Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices.

No MeSH data available.


Related in: MedlinePlus