Electron emission from conduction band of diamond with negative electron affinity

Yamaguchi, Hisato; Masuzawa, Tomoaki; Nozue, S.; Kudo, Yoshihisa; Saito, Ichitaro; Koe, Julian R.; Kudo, M.; Yamada, Takatoshi; Takakuwa, Yuji; Okano, Ken

doi:10.1103/physrevb.80.165321

Cited by 62 publications

(43 citation statements)

References 32 publications

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“…Presumably, the authentic factor that large negative bias voltage (À200 V) enhanced the EFE properties of the UNCD films is the formation of nanographite filaments, which facilitated the electrons to transport easily along the UNCD films to the emitting surface and were then emitted to vacuum without any difficulty as the diamond surfaces are NEA in nature. [54][55][56] Large enough negative bias voltage is required to produce sufficient amount of nanographitic phase to form continuous nanographitic filaments for enhancing the EFE properties.…”

Section: Discussionmentioning

confidence: 99%

Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH4/Ar plasma

Sankaran

Huang

Saravanan

et al. 2014

Journal of Applied Physics

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Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH4 and Ar under different negative bias voltages ranging from −50 to −200 V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under −200 V, the electron field emission (EFE) process can be turned on at a field as small as 4.08 V/μm, attaining a EFE current density as large as 3.19 mA/cm2 at an applied field of 8.64 V/μm. But the films grown without bias (0 V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH4/Ar plasma due to large applied bias voltage of −200 V is the prime factor, which possibly forms interconnected paths for facilitating the transport of electrons that markedly enhance the EFE properties.

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Section: Discussionmentioning

confidence: 99%

Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH4/Ar plasma

Sankaran

Huang

Saravanan

et al. 2014

Journal of Applied Physics

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“…The UP spectrum was used to determine the energies of diamond's band structure, while FE spectrum was used to determine the energy of emitted electrons relative to the diamond's band structure . In this measurement, an UP spectrum was measured while negative bias was applied on H‐terminated heavily P‐doped diamond surfaces.…”

Section: Resultsmentioning

confidence: 99%

Modification of internal barrier in hydrogen‐terminated heavily phosphorus‐doped diamond for field emission

Masuzawa

Kudo

Mimura

et al. 2016

Physica Status Solidi (a)

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In this article, a field‐induced electron emission from hydrogen (H)‐terminated surface of heavily phosphorus (P)‐doped diamond is discussed based on the barrier lowering model. Ultraviolet photoelectron spectroscopy suggested that an upward band bending of 1.45 eV existed at the surface of the diamond. A field emission characteristic as a function of the distance between an anode and diamond was measured to evaluate an average electric field in the vacuum. The barrier lowering model was introduced to estimate the reduction of the internal barrier due to the electric field at the diamond surface. The barrier lowering effect was confirmed from energies of emitted electrons, measured by combined ultraviolet photoelectron spectroscopy/field‐induced electron spectroscopy (UPS/FES). As a result, it was shown that the electron emission from n‐type diamond having NEA surface could be modulated by controlling a local electric field.

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“…Such an observation too is in accordance with the proposed model. 45 Since the graphitic phases are more conducting than the a-C phases, 46 the formation of nanographitic phases at the grain boundaries creates conduction channels for the electrons to travel through the diamond films. Hence, the primary cause for the enhancement of the EFE properties while using the negative bias voltage (À300 V) is the formation of nanographite filaments.…”

Section: Discussionmentioning

confidence: 99%

Structural modification of nanocrystalline diamond films via positive/negative bias enhanced nucleation and growth processes for improving their electron field emission properties

Saravanan

Huang

Sankaran

et al. 2015

Journal of Applied Physics

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Electron field emission (EFE) properties of nanocrystalline diamond (NCD) films synthesized by the bias-enhanced growth (beg) process under different bias voltages were investigated. The induction of the nanographitic phases is presumed to be the prime factor in enhancing the EFE properties of negative biased NCD films. Transmission electron microscopic investigations reveal that a negative bias voltage of −300 V increases the rate of growth for NCD films with the size of the grains changing from nano to ultranano size. This effect also is accompanied by the induction of nanographitic filaments in the grain boundaries of the films. The turn-on field (E0) for the EFE process then effectively gets reduced. The EFE process of the beg-NCD−300V films can be turned on at E0 = 3.86 V/μm, and the EFE current density achieved is 1.49 mA/cm2 at an applied field of 7.85 V/μm. On the other hand, though a positive-bias beg process (+200 V) results in the reduction of grain size, it does not induce sufficient nanographitic phases to lower the E0 value of the EFE process. Moreover, the optical emission spectroscopic investigation indicates that one of the primary causes that changes the granular structure of the NCD films is the increase in the proportion of C2 and CH species induced in the growing plasma. The polarity of the bias voltage is of less importance in the microstructural evolution of the films.

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Electron emission from conduction band of diamond with negative electron affinity

Cited by 62 publications

References 32 publications

Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH4/Ar plasma

Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH4/Ar plasma

Modification of internal barrier in hydrogen‐terminated heavily phosphorus‐doped diamond for field emission

Structural modification of nanocrystalline diamond films via positive/negative bias enhanced nucleation and growth processes for improving their electron field emission properties

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