I am trying to make a heat map using ggplot and geom_tiles using this code

library(readxl)
library(ggplot2)
library(dplyr)
library(reshape2)
HeLa_half_life_CpG <- read_excel("HeLa_mRNA_stability_chip1_2_combined.xlsx",
                                 sheet = "in_CpG")
melted_CpG <- melt(HeLa_half_life_CpG)
melted_CpG$Genes <- factor(melted_CpG$Genes, levels = unique(melted_CpG$Genes))
pdf("mRNA_stability_CpG.pdf", width = 3, height = 6)
ggplot(melted_CpG, aes(variable, Genes, fill= value)) + 
  geom_tile()+
  xlab("Hours")+
  ylab("")+
  labs(fill = "% mRNA remaining")+
  scale_fill_gradient(low="white",high="blue")+
  theme_minimal() +
  theme(
    text = element_text(size = 14),  # Adjust the size as needed
    axis.text.y = element_blank(), # Remove y-axis labels
    axis.text.x = element_text(size = 14),
    legend.position = "none")
dev.off()

and data:

HeLa_half_life_CpG <- structure(
  list(
    Genes = c(
      "G1",
      "G2",
      "G3",
      "G4",
      "G5",
      "G6",
      "G7",
      "G8",
      "G9",
      "G10",
      "G11",
      "G12",
      "G13",
      "G14",
      "G15",
      "G16",
      "G17",
      "G18",
      "G19",
      "G20"
    ),
    `0` = c(
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100
    ),
    `1` = c(
      116.156479707761,
      91.0127702731984,
      109.73447025453,
      86.85808192433,
      59.5598276052549,
      93.5940148082577,
      98.0985395851257,
      107.7588571215,
      117.531393141036,
      90.0590629973177,
      108.383548946902,
      63.917863771493,
      114.108148680618,
      121.850793689763,
      90.7074115232622,
      131.791958956309,
      93.4529891706761,
      67.1096649073294,
      91.4977061761886,
      86.3617500276195
    ),
    `2` = c(
      96.7597430367575,
      80.2076092386504,
      99.3294604207776,
      99.0190558569627,
      39.4558690004756,
      49.4282314951013,
      77.1264045620156,
      99.460774155045,
      96.1509176873127,
      95.0107882285699,
      82.5329765556333,
      69.2883553179083,
      77.3676845762873,
      92.8826806262721,
      83.8487800707542,
      103.838031673919,
      84.9147983928637,
      54.3747187092144,
      79.1756568571416,
      76.9389445509273
    ),
    `4` = c(
      105.737036544113,
      63.4491092110495,
      100.805427725059,
      80.2126522696507,
      72.7261380578166,
      73.3372820751092,
      87.5733427132186,
      91.0379518564103,
      106.094601401991,
      93.7441779568787,
      98.9266427305014,
      60.1007970176505,
      113.238459623547,
      113.536977434799,
      102.44403447203,
      84.1038192308167,
      90.4763264495684,
      67.2430572266142,
      99.3241885495501,
      80.2126522696507
    ),
    `6` = c(
      83.1414918304887,
      35.1886581174553,
      42.0061328645033,
      56.9562322346824,
      47.0624266352305,
      53.1744300943514,
      42.2806827525066,
      69.6664507595429,
      69.8235275169966,
      66.7802812729161,
      66.3244186525371,
      28.8009528854182,
      81.248108118721,
      72.5291077149008,
      66.1726241174151,
      61.1720516419244,
      53.0427349921935,
      39.7710647621667,
      44.6441991796653,
      51.9825894198228
    ),
    `8` = c(
      66.6264632028956,
      48.9905585191921,
      52.8504207055527,
      47.0404135186142,
      32.441664495596,
      59.3219007919469,
      44.2733303704604,
      59.994103633782,
      58.8275516186807,
      59.9935708643195,
      62.3771059829485,
      46.842598491202,
      77.2048621471892,
      68.6596073980867,
      62.0572995506867,
      46.3846777468947,
      56.2083203636403,
      45.3269453234242,
      46.2646345850238,
      58.3949960920727
    )
  ),
  row.names = c(NA, -20L),
  class = c("tbl_df", "tbl", "data.frame")
)

The heatmap has white space between the tiles of each gene.
enter image description here

I want to remove this space, please help.
This only happens when I export the file as a PDF, but when I run the command R displays the heat map with these white lines between tiles.
Thanks

I tried

geom_tile(width = 1)

but it didn’t work either.