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Reply to comment on “temperature dependence of the silicon field evaporation voltage”
Surface Science 131 (1983) L421-L422 North-Holland Publishing Company
SURFACE
SCIENCE
L42
I
LETTERS
REPLY TO COMMENT ON “TEMPERATURE SILICON FIELD EVAPORATION VOLTAGE”
DEPENDENCE
OF THE
G.L. KELLOGG Sandia National Laboratories, Received
Albuquerque,
New Mexico 87185, USA
14 June 1983
The Comment by Ernst [l] suggests that the linear relationship between the evaporation field and the temperature of a silicon sample can be explained by assuming that the silicon evaporation rate is limited by the density of holes in the space charge layer. Based on the further assumption that the density of surface states is sufficient to prevent the high electric field from perturbing the density of holes in the space charge layer, he derives an expression for the temperature dependence of the silicon evaporation field which is in good agreement with the experimental data [2]. Although this model offers a
0.8
0
100
200
300
TEMPERATURE
400
500
600
(K)
Fig. 1. The field evaporation voltage (V) normalized to the field evaporation voltage at 50 K (V,) as a function of sample temperature for silicon (III), tungsten (O), and molybdenum (A). The temperature dependences are almost identical.
0039-6028/83/0000-0000/$03.00
0 1983 North-Holland
L422
G.L. Kellogg / Temperature
dependence on Si field evaporation voltage
plausible explanation of the temperature versus voltage relationship, the data presented below suggest that the temperature dependence of field evaporation is not strongly influenced by the density of holes. In fig. 1 the previous silicon data are replotted in the form: V/V, versus temperature, where V is the evaporation to voltage at a given temperature and V, is the evaporation voltage at - 50 K. For comparison, fig. 1 also shows a plot of the same variables for tungsten [3] and molybdenum [4]. The temperature dependences for all three materials are almost identical. If the density of holes were responsible for the relationship between field and temperature as suggested by Ernst, one would not expect the same relationship to hold for metallic samples. The similarity between the results implies that the field evaporation process for silicon (in ultra-high vacuum) is qualitatively the same as that for tungsten and molybdenum and that a comprehensive theoretical description of the electric field versus temperature relationship should be equally applicable to metals and semiconductors. Unfortunately, no such theoretical description is yet available.
References [1] L. Ernst, Surface Sci. 131 (1983) 419. [2] G.L. Kellogg, Surface Sci. 124 (1982) L55. [3] The tungsten data plotted in fig. 1 were recently obtained with the background pressure below 2 x lo- lo Torr. The resulting temperature dependence, however, is only slightly different than that reported in a previous study where the background pressure was in the mid lo- lo Torr range (see ref. [3]). [4] G.L. Kellogg, J. Appl. Phys. 52 (1981) 5320.
SURFACE
SCIENCE
L42
I
LETTERS
REPLY TO COMMENT ON “TEMPERATURE SILICON FIELD EVAPORATION VOLTAGE”
DEPENDENCE
OF THE
G.L. KELLOGG Sandia National Laboratories, Received
Albuquerque,
New Mexico 87185, USA
14 June 1983
The Comment by Ernst [l] suggests that the linear relationship between the evaporation field and the temperature of a silicon sample can be explained by assuming that the silicon evaporation rate is limited by the density of holes in the space charge layer. Based on the further assumption that the density of surface states is sufficient to prevent the high electric field from perturbing the density of holes in the space charge layer, he derives an expression for the temperature dependence of the silicon evaporation field which is in good agreement with the experimental data [2]. Although this model offers a
0.8
0
100
200
300
TEMPERATURE
400
500
600
(K)
Fig. 1. The field evaporation voltage (V) normalized to the field evaporation voltage at 50 K (V,) as a function of sample temperature for silicon (III), tungsten (O), and molybdenum (A). The temperature dependences are almost identical.
0039-6028/83/0000-0000/$03.00
0 1983 North-Holland
L422
G.L. Kellogg / Temperature
dependence on Si field evaporation voltage
plausible explanation of the temperature versus voltage relationship, the data presented below suggest that the temperature dependence of field evaporation is not strongly influenced by the density of holes. In fig. 1 the previous silicon data are replotted in the form: V/V, versus temperature, where V is the evaporation to voltage at a given temperature and V, is the evaporation voltage at - 50 K. For comparison, fig. 1 also shows a plot of the same variables for tungsten [3] and molybdenum [4]. The temperature dependences for all three materials are almost identical. If the density of holes were responsible for the relationship between field and temperature as suggested by Ernst, one would not expect the same relationship to hold for metallic samples. The similarity between the results implies that the field evaporation process for silicon (in ultra-high vacuum) is qualitatively the same as that for tungsten and molybdenum and that a comprehensive theoretical description of the electric field versus temperature relationship should be equally applicable to metals and semiconductors. Unfortunately, no such theoretical description is yet available.
References [1] L. Ernst, Surface Sci. 131 (1983) 419. [2] G.L. Kellogg, Surface Sci. 124 (1982) L55. [3] The tungsten data plotted in fig. 1 were recently obtained with the background pressure below 2 x lo- lo Torr. The resulting temperature dependence, however, is only slightly different than that reported in a previous study where the background pressure was in the mid lo- lo Torr range (see ref. [3]). [4] G.L. Kellogg, J. Appl. Phys. 52 (1981) 5320.