Dual Bias Modulation Electrostatic Force Microscopy on Cu(In, Ga)Se2

Fukuzawa, Ryota; Minemoto, Takashi; Takahashi, Takuji

doi:10.1109/pvsc45281.2020.9300457

Cited by 3 publications

(4 citation statements)

References 10 publications

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“…However, in this study, the CdS film was etched out by a HCl solution to eliminate the series capacitance originating from the CdS film. The same sample was used in our previous work to investigate the frequency response of ∂C/∂V by DEFM using the V DC sweep [24,28], and we have already found that the values of V p and ∂C/∂V depended on the bias modulation frequency, where ∼1000 kHz and ∼100 kHz were chosen for the high-and low-frequency conditions, respectively. Then, we applied our PT-SCFM to this sample.…”

Section: Resultsmentioning

confidence: 99%

“…To overcome the above problem, dual bias modulation EFM (DEFM) [21][22][23][24] and broad-band EFM [25][26][27] were developed. In our previous work on DEFM [23,28], ∂C/∂V signals at high and low frequencies were acquired by sweeping a direct current (DC) bias voltage at some fixed points on the sample surface, and we focused on the DC voltage, V p , giving a peak in the ∂C/∂V curves. As illustrated in figure 1, V p corresponds to a voltage at an inflection point in the C-V curve, and if the C-V curve shifts because of, for example, the frequency response of deep levels acting as charge traps, the value of V p varies [29], as illustrated in figures 1(a) and (b).…”

Section: Introductionmentioning

confidence: 99%

“…As illustrated in figure 1, V p corresponds to a voltage at an inflection point in the C-V curve, and if the C-V curve shifts because of, for example, the frequency response of deep levels acting as charge traps, the value of V p varies [29], as illustrated in figures 1(a) and (b). Actually, the deep-level effects in the microcrystalline Cu(In, Ga)Se 2 [CIGS] material, which is a very suitable material for an absorption layer in a thin-film solar cell with high conversion efficiency [30,31], can be investigated from the experimentally acquired values of V p [28]. However, the ∂C/∂V curve must be acquired at the fixed point, as described above.…”

Section: Introductionmentioning

confidence: 99%

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Peak-tracking scanning capacitance force microscopy with multibias modulation technique

Fukuzawa¹,

Takahashi²

2022

Meas. Sci. Technol.

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Scanning capacitance force microscopy (SCFM) is a good method for capacitance measurements using electrostatic force detection. However, to obtain an entire capacitance-voltage (C-V) curve by SCFM, a sweep of a direct current (DC) bias voltage is required at a certain fixed point on a sample surface during scan suspension, and thus the measurements become very time-consuming when we want to observe some types of image related with C-V characteristics. In this paper, we propose peak-tracking scanning capacitance force microscopy (PT-SCFM) for the purpose of extracting the main feature of the C-V curve without DC voltage sweep. In PT-SCFM, alternating current voltages at three different angular frequencies, ω1 , ω2 , and ω m, are applied together with DC voltage, V DC, to generate an electrostatic force, and high-order components at the angular frequencies of ω2 -2ω1 and ω2 -2ω1 -ω m, which represent a voltage derivative of a capacitance (∂C/∂V) and a second-order derivative of the capacitance (∂2C/∂V2 ), respectively, are extracted from the electrostatic force. Then, a DC voltage, V p, giving the peak of ∂C/∂V is determined from V DC to be adjusted to nullify the ω2 -2ω1 -ω m component using a feedback controller. From the obtained values of V p and ∂C/∂V at V p, the C-V curve can be outlined. In PT-SCFM, the distributions of those values are simultaneously imaged together with a topography without V DC sweep, and when we operate PT-SCFM under various modulation frequency conditions, analyses similar to those based on the frequency dependence of the C-V property are realized. We have applied the PT-SCFM to a microcrystalline Cu(In, Ga)Se2 material to discuss the effects of surface depletion and deep-level states, from which the validity of PT-SCFM has been examined.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Peak-tracking scanning capacitance force microscopy with multibias modulation technique

Fukuzawa¹,

Takahashi²

2022

Meas. Sci. Technol.

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“…Using electrostatic force microscopy (EFM), 17) such broadband and variable frequency measurements of the capacitance-related signals have been realized by multiple bias modulation methods [18][19][20][21] or amplitude modulated voltage application techniques, 22,23) and an influence of surface states has been investigated. 20,24) Especially when the electrostaticforce modulated by the external bias between the tip and sample is detected by the frequency shift of the cantilever resonance, 25,26) which is a similar way to frequency modulation (FM)-AFM 27) and is referred to as FM-EFM here, the detected force is mainly dominated by the very local force acting on the tip itself by reducing a contribution from background force acting on the body of cantilever, 28) from which the tip-sample capacitance can be sensitively evaluated. When, however, we want to quantitatively evaluate a capacitance on a semiconductor sample by FM-EFM, the following point should be carefully taken into account:…”

Section: Introductionmentioning

confidence: 99%

Quantitative capacitance measurements in frequency modulation electrostatic force microscopy

Fukuzawa¹,

Liang²,

Shigekawa³

et al. 2022

Jpn. J. Appl. Phys.

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We have proposed a method for quantitative capacitance measurements using frequency modulation electrostatic force microscopy (EFM) with a dual bias modulation method and demonstrated it on n- and p-type Si samples. First, we theoretically derived a conversion formula from a frequency shift of cantilever resonance in EFM into a capacitance value based on the parallel plate capacitor model, by which a pair of an EFM tip and a semiconductor sample is expected to be equivalently represented. Then the capacitance measurements were experimentally conducted on the n- and p-type Si substrates, and the acquired capacitance-voltage curves indicated that the obtained capacitance values were consistent with the expected ones and that the carrier densities evaluated from the depletion capacitances were also in good agreement with those evaluated by the conventional Hall effect measurements. From those results, the validity of our quantitative evaluation method has been well confirmed.

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Accurate Electrostatic Force Measurements by Atomic Force Microscopy Using Proper Distance Control

Fukuzawa

Kobayashi

Takahashi

2023

IEEE Trans. Instrum. Meas.

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Dual Bias Modulation Electrostatic Force Microscopy on Cu(In, Ga)Se2

Cited by 3 publications

References 10 publications

Peak-tracking scanning capacitance force microscopy with multibias modulation technique

Peak-tracking scanning capacitance force microscopy with multibias modulation technique

Quantitative capacitance measurements in frequency modulation electrostatic force microscopy

Accurate Electrostatic Force Measurements by Atomic Force Microscopy Using Proper Distance Control

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